chapter 4 part c: fuel and exhaust systems - multi-point...

4C•1

Chapter 4 Part C: Fuel and exhaust systems -multi-point fuel injection modelsContentsACAV intake system (1998 cc 16-valve models) - general

information, removal and refitting 19Accelerator cable - removal, refitting and adjustment 3Accelerator pedal - removal and refitting 4Air cleaner assembly and intake ducts - removal and refitting 2Air cleaner filter element renewal See Chapter 1Bosch Motronic M1.3 system components - removal and refitting . . . 15Bosch Motronic MP3.1 system components - removal and refitting .. 14Bosch Motronic MP3.2 system components - removal and refitting .. 16Bosch Motronic MP5.1 system components - removal and refitting .. 13Exhaust manifold - removal and refitting 20Exhaust system - general information, removal and refitting 21Exhaust system check See Chapter 1Fuel filter - renewal See Chapter 1

Degrees of difficulty

Fuel gauge sender unit - removal and refitting 9Fuel injection system - depressurisation 7Fuel injection system - testing and adjustment 11Fuel injection systems - general information 6Fuel pump - removal and refitting 8Fuel tank - removal and refitting 10General fuel system checks See Chapter 1General information and precautions 1Idle speed and mixture adjustment See Chapter 1Inlet manifold - removal and refitting 18Magneti Marelli 8P.20 system components - removal and refitting . 17Throttle housing - removal and refitting 12Unleaded petrol - general information and usage 5

Easy, suitable fornovice with littleexperience

Fairly easy, suitablefor beginner withsome experience

Fairly difficult, suitablefor competent DIYmechanic

Difficult, suitable forexperienced DIYmechanic

Very difficult,suitable for expert DIYor professional

SpecificationsSystem type1761 cc (LFZ engine) models Bosch Motronic MP5.11905 cc non-catalyst (D6E engine) models Bosch Motronic MP3.11905 cc catalyst (DKZ engine) models Bosch Motronic M1.31998 cc 8-valve (RFX engine) models Magneti Marelli 8P.201998 cc 16-valve (RFY engine) models Bosch Motronic MP3.2Note: Refer to Chapter 2B for further information on engine code identification

Fuel system dataFuel pump type Electric, immersed in tankFuel pump regulated constant pressure (at specified idle speed):

Bosch Motronic systems 2.5 to 3.0 bars (depending on system)Magneti Marelli system 2.0 bars

Specified idle speed:1905 cc models 850 ± 50 rpm (adjustable via screw on the throttle housing)All other models -. 850 ± 50 rpm (not adjustable -controlled by ECU)

Idle mixture CO content:1905 cc non-catalyst (D6E engine) models 1.0 to 2.0 % (adjustable via screw on mixture adjustment -

potentiometer)1905 cc catalyst (DKZ engine) models, and all other models Less than 1.0 % (not adjustable- controlled by ECU)

Recommended fuelMinimum octane rating:

1905 cc non-catalyst (D6E engine) models 95 RON unleaded (UK unleaded premium) or97 RON leaded (UK "4-star")

1905 cc catalyst (DKZ engine) models, and all other models 95 RON unleaded (UK unleaded premium).Leaded fuel must not be used

4C•2 Fuel and exhaust systems - multi-point fuel injection models

Torque wrench settings Nm ibf ftInlet manifold nuts 22 16Exhaust manifold nuts 22 16Exhaust system fasteners:

Front pipe-to-manifold nuts 10 7Clamping ring nut(s):

Clamps secured with one bolt 25 18Clamps secured with two bolts 20 15

The fuel supply system consists of a fueltank (which is mounted under the rear of thecar, with an electric fuel pump immersed in it),a fuel filter, fuel feed and return lines. The fuelpump supplies fuel to the fuel rail, which actsas a reservoir for the four fuel injectors whichinject fuel into the inlet tracts. The fuel filterincorporated in the feed line from the pump tothe fuel rail ensures that the fuel supplied tothe injectors is clean.

Refer to Section 6 for further information onthe operation of each fuel injection system,and to Section 21 for information on theexhaust system. Throughout this Section, it isalso occasionally necessary to identifyvehicles by their engine codes rather than byengine capacity alone. Refer to the relevantPart of Chapter 2 for further information onengine code identification.

Warning: Many of the proceduresin this Chapter require theremoval of fuel lines and

connections, which may result in some fuelspillage. Before carrying out any operationon the fuel system, refer to the precautionsgiven in "Safety first!" at the beginning ofthis manual, and follow them implicitly.Petrol is a highly-dangerous and volatileliquid, and the precautions necessary whenhandling it cannot be overstressed.Note: Residual pressure will remain in the fuellines long after the vehicle was last used. Whendisconnecting any fuel line, first depressurisethe fuel system as described in Section 7.

Removal1761 cc and 1998 cc 8-valve models1 Slacken the retaining clip, and disconnectthe breather hose(s) from the side of the air

2.1a On 1761 cc and 1998 cc 8-valvemodels, slacken the clips and disconnectthe hose(s) from the air cleaner-to-throttle

body duct . . .2.1b . . . then slacken the duct retaining

cl ips . . .

cleaner-to-throttle housing duct. Slacken theduct retaining clips, then disconnect it fromthe air cleaner and throttle housing, andremove it from the vehicle (see illustrations).

Where necessary, recover the rubber sealingring from the throttle housing.2 Release the two retaining clips, thenslacken and remove the two retaining screwsfrom the front of the cylinder head cover, andremove the air cleaner element cover from thehead. Withdraw the air cleaner element.3 To remove the intake duct, undo the boltsecuring the rear section of the duct to theend of the cylinder head, then slacken theretaining clip and disconnect the duct fromthe cylinder head cover. Undo the nutsecuring the front of the duct to the left-handwing valance, and manoeuvre the duct out ofthe engine compartment (see illustration).

1905 cc models4 Slacken the retaining clips, and disconnectthe intake duct and throttle housing duct fromthe air cleaner (see illustration).5 Slacken and remove the bolt securing theair cleaner right-hand mounting bracket to therear of the cylinder head, and the two nutssecuring the housing to its left-hand mountingbracket. Lift the air cleaner housing out of theengine compartment (see illustrations).6 To remove the intake duct, undo the nut(s)securing the front of the duct to the left-handwing valance, then undo the nut securing theduct to its mounting bracket (where fitted).Disconnect the duct from the air cleanerhousing, if not already having done so, andremove it from the vehicle.7 On models without a catalytic converter(Bosch Motronic MP3.1 system), to removethe air cleaner-to-throttle housing duct, first

2.1c . . . and remove the duct from theengine compartment

2.3 Intake duct front retaining nut

2.4 On 1905 cc models, slacken theretaining clips and disconnect the intakeand throttle housing ducts from the air

cleaner.. .

1 General information andprecautions

2 Air cleaner assembly and intakeducts - removal and refitting

Fuel and exhaust systems - multi-point fuel injection models 4C•3

2.5a . . . then undo the retaining bolt(arrowed)...

disconnect the wiring connector from theintake air temperature sensor. Slacken theretaining clip, and disconnect the vacuumpipe from the front of the duct. Slacken theclips, disconnect the duct from the air cleanerand throttle housings, and remove the duct.Recover the rubber sealing ring from thethrottle housing.8 On models with a catalytic converter(Bosch Motronic M1.3 system), the aircleaner-to-throttle housing duct is in twosections, with the airflow meter situated in themiddle. Each section can be removed once itsretaining clips have been slackened, notingthat, in the case of the front duct section, itwill also be necessary to disconnect thevacuum pipe.

1998 cc 16-valve models9 Slacken the retaining clip, and disconnectthe air cleaner-to-throttle housing duct fromthe throttle housing. Recover the rubbersealing ring. Release the retaining clips, anddisconnect the breather hose(s) from the duct.10 Apply the handbrake, then jack up thefront of the vehicle and support it on axlestands.11 From underneath the vehicle, slacken andremove the retaining nuts securing theresonator chamber to the side of the aircleaner housing, and remove the chamber.12 Undo the air cleaner housing retainingbolt(s), and remove the housing and ductassembly from underneath the vehicle.

Refitting13 Refitting is a reversal of the removalprocedure, ensuring that all hoses areproperly reconnected, and that all ducts arecorrectly seated and securely held by theirretaining clips.

3 Accelerator cable - removal,refitting and adjustment

1 Refer to Chapter 4A, Section 7, substituting"throttle housing" for all references to thecarburettor. On models with automatictransmission, once the accelerator cable iscorrectly adjusted, check the kickdown cableadjustment as described in Chapter 7B.

2.5b . . . and the two retaining nuts(locations arrowed), then remove the air

cleaner housing

Refer to Chapter 4A, Section 8.

Note: The information given in this Chapter iscorrect at the time of writing. If updatedinformation is thought to be required, checkwith a Citroen dealer. If travelling abroad,consult one of the motoring organisations (or asimilar authority) for advice on the fuel available.1 The fuel recommended by Citroen is givenin the Specifications Section of this Chapter,followed by the equivalent petrol currently onsale in the UK.2 All Citroen ZX multi-point injection modelsare designed to run on fuel with a minimumoctane rating of 95 (RON). With the exceptionof those 1905 cc models without a catalyticconverter (Bosch Motronic MP3.1 system), allmodels have a catalytic converter, and somust be run on unleaded fuel only. Under nocircumstances should leaded fuel (UK "4-star")be used, as this may damage the converter.However, 1905 cc models without a catalyticconverter can use either unleaded or leadedfuel without modification or risk of damage.3 Super unleaded petrol (98 octane) can alsobe used in all models if wished, though thereis no advantage in doing so.

Bosch Motronic MP5.1 system -1761 cc models1 The Bosch Motronic engine management(fuel injection/ignition) system is fitted to all1761 cc models. The system incorporates aclosed-loop catalytic converter and anevaporative emission control system, andcomplies with the very latest emission controlstandards. Refer to Chapter 5 for informationon the ignition side of the system; the fuel side

of the system operates as follows.2 The fuel pump (which is immersed in thefuel tank) supplies fuel from the tank to thefuel rail, via a filter mounted underneath therear of the vehicle. Fuel supply pressure iscontrolled by the pressure regulator in the fuelrail. When the optimum operating pressure ofthe fuel system is exceeded, the regulatorallows excess fuel to return to the tank.3 The electrical control system consists of theECU, along with the following sensors:(a) Throttle potentiometer - informs the ECU

of the throttle position, and the rate ofthrottle opening/closing.

(b) Coolant temperature sensor - informs theECU of engine temperature.

(c) Intake air temperature sensor - informsthe ECU of the temperature of the airpassing through the throttle housing.

(d) Lambda sensor - informs the ECU of theoxygen content of the exhaust gases(explained in greater detail in Part D ofthis Chapter).

(e) Crankshaft sensor - informs the ECU ofthe crankshaft position and speed ofrotation.

(f) Manifold Absolute Pressure (MAP) sensor- informs the ECU of the load on theengine (expressed in terms of inletmanifold vacuum).

(g) Vehicle speed sensor - informs the ECUof the vehicle speed.

4 All the above signals are analysed by the ECU,and it selects the fuelling response appropriate tothose values. The ECU controls the fuel injectors(varying the pulse width - the length of time theinjectors are held open - to provide a richer orweaker mixture, as appropriate). The mixture isconstantly varied by the ECU, to provide the bestsetting for cranking, starting (with either a hot orcold engine), warm-up, idle, cruising, andacceleration.5 The ECU also has full control over theengine idle speed, via an auxiliary air valvewhich bypasses the throttle valve. When thethrottle valve is closed, the ECU controls theopening of the valve, which in turn regulatesthe amount of air entering the manifold, andso controls the idle speed.6 The ECU also controls the exhaust andevaporative emission control systems, whichare described in detail in Part D of thisChapter.7 An electric heating element is fitted to thethrottle housing; the heater is supplied withcurrent by the ECU, and warms the throttlehousing on cold starts to prevent possibleicing of the throttle valve.8 If there is an abnormality in any of thereadings obtained from either the coolanttemperature sensor, the intake airtemperature sensor or the lambda sensor, theECU enters its back-up mode. In this event, itignores the abnormal sensor signal, andassumes a pre-programmed value which willallow the engine to continue running (albeit atreduced efficiency). If the ECU enters thisback-up mode, the warning light on the

4 Accelerator pedal -removal and refitting

5 Unleaded petrol - generalinformation and usage

6 Fuel injection systems - generalinformation


instrument panel will come on, and therelevant fault code will be stored in the ECUmemory.9 If the warning light comes on, the vehicleshould be taken to a Citroen dealer at theearliest opportunity. A complete test of theengine management system can then becarried out, using a special electronicdiagnostic test unit which is simply pluggedinto the system's diagnostic connector.

Bosch Motronic MP3.1 system -1905 cc models without a catalyticconverter10 The Bosch Motronic MP3.1 enginemanagement (fuel injection/ignition) system isfitted to all 1905 cc models without a catalyticconverter (D6E engine). Refer to Chapter 5 forinformation on the ignition side of the system.11 The MP3.1 system is very similar inoperation to the MP5.1 system describedabove, noting the following differences:(a) On the MP3.1 system, there is no lambda

(oxygen) sensor or vehicle speed sensor.The idle mixture (exhaust gas CO content)can be manually adjusted via the mixtureadjustment potentiometer.

(b) The ECU has no control over the engineidle speed; the idle speed is manually setusing a screw on the throttle housing. Anauxiliary air valve (not to be confused withthe idle speed control valve on the MP5.1system) is incorporated in the system, butthis is used purely as an additional airsupply on cold starts and during thewarm-up period.

(c) There is no heating element fitted to thethrottle housing. The engine coolant iscirculated around the housing, to warmthe housing after cold starts.

(d) There is no evaporative emission controlsystem.

Bosch Motronic Ml.3 system -1905 cc models with a catalyticconverter12 The Bosch Motronic M1.3 enginemanagement (fuel injection/ignition) system isfitted to all 1905 cc models with a catalyticconverter (DKZ engine). Refer to Chapter 5 forinformation on the ignition side of the system.13 The M1.3 system is very similar inoperation to the MP5.1 system describedabove, noting the following differences:(a) On the M1.3 system, there is no vehicle

speed sensor or MAP sensor. In place ofthe MAP sensor, an airflow meter is fittedto the throttle housing intake duct, toinform the ECU of the volume of airpassing through the duct and entering thethrottle housing.

(b) The ECU has no control over the engineidle speed; the idle speed is manually setusing a screw on the throttle housing. Anauxiliary air valve (not to be confused withthe idle speed control valve on the MP5.1system) is incorporated in the system, butthis is used purely as an additional air

supply on cold starts and during thewarm-up period.

(c) There is no heating element fitted to thethrottle housing. The engine coolant iscirculated around the housing, to warmthe housing after cold starts.

Bosch Motronic MP3.2 system -1998 cc 16-valve models14 The Bosch Motronic MP3.2 enginemanagement (fuel injection/ignition) system isfitted to all 1998 cc 16-valve models. Refer toChapter 5 for information on the ignition sideof the system.15 The MP3.2 system is very similar inoperation to the MP5.1 system describedabove, noting that, in addition to the sensorslisted, a camshaft position sensor isincorporated into the system. The camshaftposition sensor is fitted to the left-hand end ofthe cylinder head, directly over the top of theinlet camshaft, and informs the ECU whenNo 1 cylinder is at Top Dead Centre (TDC).16 The MP3.2 system differs from all theother fuel injection systems in that it is a"sequential" system. This means that each ofthe four fuel injectors is triggered individually,just before the inlet valve on that particularcylinder opens. This is in contrast to all othersystems, on which all four injectors aretriggered simultaneously; this happens oncefor every revolution of the crankshaft.

Magneti Marelli 8P.20 system -1998 cc 8-valve models17 The Magneti Marelli 8P.20 enginemanagement (fuel injection/ignition) system isfitted to all 1998 cc 8-valve models. Refer toChapter 5 for information on the ignition sideof the system.18 The system is very similar in operation tothe Bosch MP5.1 system described above,apart from the idle speed control system.19 On the Magneti Marelli system, the idlespeed is controlled by the ECU via a steppermotor fitted to the throttle housing. The motorhas a pushrod controlling the opening of anair passage which bypasses the throttle valve.When the throttle valve is closed, the ECUcontrols the movement of the motor pushrod,which regulates the amount of air which flowsthrough the throttle housing passage, socontrolling the idle speed. The bypasspassage is also used as an additional airsupply during cold starting.

Note: Refer to the warning note in Section 1before proceeding.

Warning: The followingprocedure will merely relieve thepressure in the fuel system -remember that fuel will still be

present in the system components andtake precautions accordingly beforedisconnecting any of them.

1 The fuel system referred to in this Section isdefined as the tank-mounted fuel pump, thefuel filter, the fuel injectors, the fuel rail andthe pressure regulator, and the metal pipesand flexible hoses of the fuel lines betweenthese components. All these contain fuelwhich will be under pressure while the engineis running, and/or while the ignition isswitched on. The pressure will remain forsome time after the ignition has beenswitched off, and it must be relieved in acontrolled fashion when any of thesecomponents are disturbed for servicing work.

2 Disconnect the battery negative terminal.3 Place a container beneath theconnection/union to be disconnected, andhave a large rag ready to soak up anyescaping fuel not being caught by thecontainer.4 Slowly loosen the connection or union nutto avoid a sudden release of pressure, andposition the rag around the connection, tocatch any fuel spray which may be expelled.Once the pressure is released, disconnect thefuel line. Plug the pipe ends, to minimise fuelloss and prevent the entry of dirt into the fuelsystem.

8 Fuel pump -removal and refitting

Note: Refer to the warning note in Section 1before proceeding.

Removal1 Disconnect the battery negative lead.2 For access to the fuel pump, tilt or removethe rear seats, as described in Chapter 11.3 Using a screwdriver, carefully prise theplastic access cover from the floor, to exposethe fuel pump (located under the right-handcover).4 Disconnect the wiring connector from thefuel pump, and tape the connector to thevehicle body, to prevent it disappearingbehind the tank.5 Mark the hoses for identification purposes,then slacken the feed and return hoseretaining clips. Where the original crimped-type Citroen hose clips are fitted, cut the clipsand discard them; use standard worm-drivehose clips on refitting. Disconnect both hosesfrom the top of the pump, and plug the hoseends.6 Noting the alignment marks on the tank,pump cover and the locking ring, unscrew thering and remove it from the tank. This is bestaccomplished by using a screwdriver on theraised ribs of the locking ring, as follows.Carefully tap the screwdriver to turn the ringanti-clockwise until it can be unscrewed byhand.7 Displace the pump cover, then reach into thetank and unclip the pump from the tank base.Carefully lift the fuel pump assembly out of thefuel tank, taking care not to damage the filter,or to spill fuel onto the interior of the vehicle.

7 Fuel system - depressurisation


Recover the rubber sealing ring and discard it -a new one must be used on refitting.8 Note that the fuel pump is only available asa complete assembly - no components areavailable separately.

Refitting9 Ensure the fuel pump pick-up filter is cleanand free of debris. Fit the new sealing ring tothe top of the fuel tank.10 Carefully manoeuvre the pump assemblyinto the fuel tank, and clip it into position inthe base of the tank.11 Align the mark on the fuel pump coverwith the centre of the three alignment markson the fuel tank, then refit the locking ring.Securely tighten the locking ring, and checkthat the locking ring, pump cover and tankmarks are all correctly aligned.12 Reconnect the feed and return hoses tothe top of the fuel pump, using the marksmade on removal to ensure they correctlyreconnected, and securely tighten theirretaining clips.13 Reconnect the pump wiring connector.14 Reconnect the battery negative terminal,and start the engine. Check the fuel pumpfeed and return hoses unions for signs ofleakage.15 If all is well, refit the plastic access cover,and tilt or refit the rear seat as described inChapter 11 (as applicable).

9 Fuel gauge sender unit -removal and refitting

Refer to Chapter 4A, Section 5, noting thatthere are no fuel pipe connections to thesender unit.

10 Fuel tank -removal and refitting

Refer to Chapter 4A, Section 6, noting thatit will be necessary to depressurise the fuelsystem as the feed and return hoses aredisconnected (see Section 7). It will also benecessary to disconnect the wiring connectorfrom the fuel pump before lowering the tankout of position (see Section 8).

11 Fuel injection system -testing and adjustment

Testing1 If a fault appears in the fuel injectionsystem, first ensure that all the system wiringconnectors are securely connected and freeof corrosion. Ensure that the fault is not due topoor maintenance; ie, check that the aircleaner filter element is clean, the spark plugsare in good condition and correctly gapped,the cylinder compression pressures arecorrect, the ignition timing is correct, and thatthe engine breather hoses are clear andundamaged, referring to Chapters 1, 2 and 5for further information.2 If these checks fail to reveal the cause ofthe problem, the vehicle should be taken to asuitably-equipped Citroen dealer for testing. Awiring block connector is incorporated in theengine management circuit, into which aspecial electronic diagnostic tester can beplugged; the connector is located inside eitherthe engine compartment junction box, ordirectly in front of the box (see illustration).The tester will locate the fault quickly andsimply, alleviating the need to test all thesystem components individually, which is atime-consuming operation that carries a riskof damaging the ECU.

Adjustment3 On 1905 cc models without a catalyticconverter (Motronic MP3.1 system), both theidle speed and idle mixture (exhaust gas COlevel) are adjustable. On 1905 cc models witha catalytic converter (Motronic M1.3 system),only the idle speed is adjustable (mixtureadjustment is not possible). Refer to Chapter1 for information on adjustment procedures.4 On all other models, experienced homemechanics with a considerable amount of skilland equipment (including a tachometer andan accurately calibrated exhaust gas analyser)may be able to check the exhaust CO leveland the idle speed. However, if these arefound to be in need of adjustment, the carmust be taken to a suitably-equipped Citroendealer for further testing. Neither the mixture

adjustment (exhaust gas CO level) nor the idlespeed are adjustable, and should either beincorrect, a fault must be present in the fuelinjection system.

Removal1 Disconnect the battery negative terminal.

1761 cc and 1998 cc 8-valve models2 Remove the air cleaner-to-throttle housingduct as described in Section 2.3 Disconnect the accelerator inner cable fromthe throttle cam, then withdraw the outercable from the mounting bracket, along withits flat washer and spring clip (seeillustration).4 Depress the retaining clips, and disconnectthe wiring connectors from the throttlepotentiometer, the electric heating element,the air temperature sensor and idle controlstepper motor (as applicable) (seeillustration).5 Release the retaining clips (where fitted),and disconnect all the relevant vacuum andbreather hoses from the throttle housing (seeillustration). Make identification marks on thehoses, to ensure they are connected correctlyon refitting.6 Slacken and remove the three retainingscrews, and remove the throttle housing from

11.2 Diagnostic wiring connector locatedin the engine compartment junction box

12.3 Disconnecting the accelerator cable -1998 cc 8-valve model

12.4 Throttle housing wiring connectors(arrowed) -1761 cc model

12.5 Throttle housing vacuum hoses(arrowed) - 1761 cc model

12 Throttle housing -removal and refitting


12.7a On 1905 cc models, slacken theretaining clip . . .

12.8b . . . then undo the retaining nut andbolt (arrowed)...

12.8c . . . and remove the bracket.Remove the flat washer (arrowed) for

safekeeping

12.7b . . . then disconnect the duct andrecover the rubber sealing ring

the inlet manifold. Remove the O-ring from themanifold, and discard it - a new one must beused on refitting.

1905 cc models7 Slacken the retaining clip, disconnect theintake duct from the end of the throttlehousing, and recover the rubber sealing ring(where fitted) (see illustrations).8 Disconnect the accelerator inner cable fromthe throttle cam. Slacken and remove the boltand nut securing the outer cable mountingbracket to the manifold, then withdraw thebracket. Remove the flat washer from the endof the cable for safekeeping (seeillustrations). On models with automatictransmission, free the kickdown cable fromthe throttle cam.9 Depress the retaining clip, and disconnectthe wiring connector from the throttlepotentiometer (see illustration).10 Relieve any pressure in the coolingsystem by unscrewing the filler cap. Slackenthe retaining clips, and disconnect the twocoolant hoses from the base of the throttlehousing. Plug the hose ends, working quicklyto minimise coolant loss.11 Release the retaining clips (where fitted),and disconnect all the relevant vacuum andbreather hose(s) from the throttle housing(see illustration). Make identification markson the hoses, to ensure they are correctlyreconnected on refitting.12 Undo the remaining two retaining nuts,

12.8a Disconnect the accelerator cablefrom the throttle cam . . .

and remove the throttle housing from themanifold. On early models, it will also benecessary to remove the nut and bolt securingthe base of the housing to its support bracket(see illustration). Remove the O-ring from themanifold, and discard it - a new one must beused on refitting.

1998 cc 16-valve models13 Slacken the retaining clip, disconnect theintake duct from the end of the throttlehousing, and recover the rubber sealing ring(where fitted).14 Disconnect the accelerator inner cablefrom the throttle cam, then withdraw the outercable from the mounting bracket, along withits flat washer and spring clip.15 Depress the retaining clips, anddisconnect the wiring connectors from thethrottle potentiometer, the electric heatingelement, and the air temperature sensor.16 Slacken the retaining clips (where fitted),and disconnect all the relevant vacuum andbreather hoses from the throttle housing.Make identification marks on the hoses, toensure they are connected correctly onrefitting.17 Slacken the nut securing the throttlehousing lower mounting bracket to thetransmission housing.18 Slacken and remove the housing retainingscrews, then remove the throttle housing fromthe inlet manifold. Remove the O-ring from themanifold, and discard it - a new one must beused on refitting.

12.9 Disconnect the throttle potentiometerwiring connector . . .

12.11 . . . and the breather hose from thethrottle housing

12.12 Undo the two remaining nuts, andremove the throttle housing


13.3 Wiring tray retaining bolt (1) andinjector wiring connectors (2) - 1761 cc

model

Refitting19 Refitting is a reversal of the removalprocedure, noting the following points:(a) Fit a new O-ring to the manifold, then refit

the throttle housing and securely tightenits retaining nuts or screws (asapplicable).

(b) Ensure all hoses are correctlyreconnected and, where necessary, aresecurely held in position by the retainingclips.

(c) Ensure all wiring is correctly routed, andthat the connectors are securelyreconnected.

(d) On completion, adjust the acceleratorcable as described in Section 3.

(e) On 1905 cc models, check the coolantlevel and top up if necessary (Chapter 1).

13 Bosch Motronic MP5.1system components -removal and refitting

Note: Check parts availability with a Citroendealer prior to removing individual components.At the time of writing, certain components areonly available as part of a larger assembly - egthe throttle potentiometer is only available aspart of the throttle housing assembly.

Fuel injectorsNote: Refer to the warning note in Section 1before proceeding. If a faulty injector issuspected, before condemning the injector, itis worth trying the effect of one of theproprietary injector-cleaning treatments.1 Disconnect the battery negative terminal.2 Remove the air cleaner-to-throttle housingduct as described in Section 2.3 Undo the two bolts securing the wiring trayto the top of the manifold, and position thetray clear of the injectors (see illustration).4 Depress the retaining clip(s), anddisconnect the wiring connector(s) from theinjector(s).5 Slacken the retaining screw, and removethe injector retaining plate; Nos 1 and 2injectors are retained by one plate, Nos 3 and4 by another.

13.17 Idle speed auxiliary air valve -1761 cc model

6 Place a wad of clean rag over the injector,to catch any fuel spray which may bereleased, then carefully ease the relevantinjector(s) out of the manifold. Remove the O-ring from the end of each disturbed injector,and discard it - these must be renewedwhenever they are disturbed.7 On refitting the injectors, fit a new O-ring tothe end of each injector. Apply a smear ofengine oil to the O-ring, to aid installation,then ease the injector(s) back into position inthe manifold.8 Ensure each injector connector is pointingupwards, then refit the retaining plate andsecurely tighten its retaining screw.Reconnect the wiring connector(s) to theinjector(s).9 Refit the wiring tray to the top of themanifold, and securely tighten its retainingbolts.10 Refit the air cleaner-to-throttle body duct,and reconnect the battery. Start the engine,and check the injectors for signs of leakage.

Fuel pressure regulator11 Refer to Section 14.

Throttle potentiometer12 The throttle potentiometer is fitted to theright-hand side of the throttle housing. Toremove the potentiometer, first disconnect thebattery negative terminal.13 Depress the retaining clip, and disconnectthe potentiometer wiring connector.14 Slacken and remove the two retainingscrews, and remove the potentiometer fromthe throttle housing.15 Refitting is the reverse of removal,ensuring that the potentiometer is correctlyengaged with the throttle valve spindle.

Electronic Control Unit (ECU)16 Refer to Section 17.

Idle speed auxiliary air valve17 The idle speed auxiliary air valve ismounted on the left-hand end of the cylinderhead, directly above the ignition HT coil (seeillustration). To remove the valve, firstdisconnect the battery negative terminal.

13.22 MAP sensor wiring connector (1),vacuum hose (2) and retaining nut (3) -

1761 cc model

18 Depress the retaining clip, and disconnectthe wiring connector from the top of the valve.19 Slacken the retaining clip(s), anddisconnect the two hoses from the valve.Slide the valve rubber retaining clip off itspegs, and remove the valve from the enginecompartment.20 Refitting is a reverse of the removalsequence, ensuring that the hoses aresecurely reconnected.

Manifold absolute pressure (MAP)sensor21 The MAP sensor is situated on the right-hand side of the engine compartment,attached to the engine/transmission mountingpoint. To remove the MAP sensor, firstdisconnect the battery negative terminal.22 Depress the retaining clip, disconnect thewiring connector from the sensor, thendisconnect the vacuum hose from the sensor(see illustration).23 Undo the retaining bolt, and remove thesensor from the engine compartment.24 Refitting is a reverse of the removalprocedure.

Coolant temperature sensor25 Refer to Chapter 3, Section 6.

Intake air temperature sensor26 The intake air temperature sensor islocated in the throttle housing (seeillustration).

13.26 On 1761 cc models, the intake airtemperature sensor (arrowed) is situated

behind the throttle potentiometer


14.3 Where original crimped-type Citroenhose clips are fitted, cut them and discard

27 To remove the sensor, first remove thethrottle potentiometer as described inparagraphs 12 to 14.28 Depress the retaining clip, and disconnectthe wiring connector from the air temperaturesensor.29 Remove the screw securing the sensorconnector to the top of the throttle housing,then carefully ease the sensor out of positionand remove it from the throttle housing.Examine the sensor O-ring for signs ofdamage or deterioration, and renew ifnecessary.30 Refitting is a reversal of the removalprocedure, using a new O-ring wherenecessary, and ensuring that the throttlepotentiometer is correctly engaged with thethrottle valve spindle.

Crankshaft sensor31 Refer to Section 14.

Fuel injection system relay unit32 Refer to Section 14.

Throttle housing heating element33 Refer to Section 17.

Note: Check parts availability with a Citroendealer prior to removing individualcomponents. At the time of writing, certaincomponents are only available as part of alarger assembly - eg the throttle potentiometeris only available as part of the throttle housingassembly.

Fuel rail and injectorsNote: Refer to the warning note in Section 1before proceeding. If a faulty injector issuspected, before condemning the injector, itis worth trying the effect of one of theproprietary injector-cleaning treatments.1 Disconnect the battery negative terminal.2 Disconnect the vacuum pipe from the fuelpressure regulator.3 Bearing in mind the information given in

14.4 Disconnecting the injector wiringconnectors -1905 cc model

Section 7, slacken the retaining clips, anddisconnect the fuel feed and return hosesfrom the either end of the fuel rail. Where theoriginal crimped-type Citroen hose clips arestill fitted, cut them off and discard them; usestandard worm-drive hose clips on refitting(see illustration).4 Depress the retaining tangs, anddisconnect the wiring connectors from thefour injectors (see illustration).5 Slacken and remove the two fuel railretaining bolts, then carefully ease the fuel railand injector assembly out from the inletmanifold and remove it from the vehicle (seeillustration). Remove the O-rings from theend of each injector, and discard them; thesemust be renewed whenever they aredisturbed.6 Slide out the retaining clip(s), and removethe relevant injector(s) from the fuel rail.Remove the upper O-ring from each injectoras it is removed, and discard it; all O-ringsmust be renewed once they have beendisturbed.7 Refitting is a reversal of the removalprocedure, noting the following points:(a) Fit new O-rings to all disturbed injectors.(b) Apply a smear of engine oil to the O-rings

to aid installation, then ease the injectorsand fuel rail into position, ensuring thatnone of the O-rings are displaced.

(c) On completion, start the engine andcheck for fuel leaks.

14.5 On 1905 cc models, the fuel rail isretained by two bolts (arrowed)

Fuel pressure regulatorNote: Refer to the warning note in Section 1before proceeding.8 Disconnect the vacuum pipe from theregulator.9 Place a wad of clean rag over the regulator,to catch any fuel spray which may bereleased. Remove the retaining clip, and slidethe regulator out of the end of the fuel rail (seeillustration).10 Refitting is a reversal of the removalprocedure. Examine the regulator seal forsigns of damage or deterioration, and renew ifnecessary.

Throttle potentiometer11 Disconnect the battery negative terminal.12 Depress the retaining clip, and disconnectthe wiring connector from the throttlepotentiometer.13 Slacken and remove the two retainingscrews, then disengage the potentiometerfrom the throttle valve spindle and remove itfrom the vehicle (see illustration).14 Refitting is a reverse of the removalprocedure, ensuring that the potentiometer iscorrectly engaged with the throttle valvespindle (see illustration).

Electronic Control Unit (ECU)15 The ECU is located in the rear left-handcorner of the engine compartment. To remove

14.9 Fuel pressure regulator retaining clip(arrowed) can be prised out of position

using a flat-bladed screwdriver

14.13 Throttle potentiometer is secured tothe throttle housing by two screws



14.14 On refitting, ensure that thepotentiometer is correctly engaged with 14.17a Undo the ECU upper retaining

the throttle valve spindle (arrowed) bo l t . . .

the ECU, first disconnect the battery negativeterminal.16 Depress the retaining clip, and disconnectthe wiring connector from the idle mixtureadjustment potentiometer.17 Slacken and remove the upper boltsecuring the ECU mounting bracket to thewing valance, then loosen the lower bolt(there is no need to remove the lower bolt, asthe mounting is slotted). Withdraw the bracketand ECU assembly from the enginecompartment, disconnecting the wiringconnector and vacuum pipe from the ECU asthey become accessible (see illustrations).18 With the assembly on the bench, undo thebolts securing the ECU to the bracket, andseparate the two components.19 Refitting is a reversal of the removalprocedure, ensuring that the wiring connectorand vacuum pipe are securely reconnected.

Idle speed mixture adjustmentpotentiometer20 The idle speed mixture adjustmentpotentiometer is situated in the rear left-handcorner of the engine compartment, mountedonto the ECU bracket. To remove it, firstdisconnect the battery negative terminal.21 Depress the retaining tangs anddisconnect the wiring connector, then undo theretaining screw and remove the potentiometerfrom the vehicle (see illustrations).22 Refitting is the reverse of removal. Oncompletion, check and, if necessary, adjust

14.21b . . . then undo the retaining screwand remove the idle speed mixture

potentiometer

the idle mixture setting (exhaust gas CO level)as described in Chapter 1.

Auxiliary air valve23 The auxiliary air valve is mounted on theleft-hand end of the cylinder head, directlybeneath the ignition HT coil (see illustration).24 To improve access to the valve, removethe ignition HT coil as described in Chapter 5.25 Depress the retaining clip, and disconnectthe wiring connector from the air valve.26 Slacken the retaining clips, anddisconnect the vacuum hoses from either endof the auxiliary air valve.27 Undo the two retaining bolts, and removethe auxiliary air valve from the enginecompartment.28 Refitting is a reversal of the removalprocedure.

Manifold absolute pressure (MAP)sensor29 The MAP sensor is an integral part of theelectronic control unit (ECU). Refer toparagraphs 15 to 19 for removal and refittingdetails.


Intake air temperature sensor31 The intake air temperature sensor islocated in the air cleaner-to-throttle housingduct (see illustration). To remove the sensor,first disconnect the battery negative terminal.

14.17b . . . and loosen its lower mountingnut. The lower mounting is slotted to ease

removal

14.17c Remove the ECU, disconnecting itsvacuum hose (1) and wiring connector (2)

as they become accessible

14.21a Disconnect the wiringconnector...

14.23 Auxiliary air valve location - wiringconnector arrowed

14.31 Disconnecting the wiring connectorfrom the intake air temperature sensor


32 Disconnect the wiring connector, thenunscrew the sensor from the intake duct andremove it from the vehicle.33 Refitting is the reverse of removal.

Crankshaft sensor34 The crankshaft sensor is mounted on topof the transmission housing, next to the left-hand end of the cylinder block. To remove thesensor, first disconnect the battery negativeterminal.35 Access to the sensor is poor, and it will benecessary to remove the battery and batterytray (see Chapter 5) and/or the intake ductassembly (see Section 2) to improve access(depending on model and specification). Onsome models, it will also be necessary toremove the metal plate from the top of thetransmission housing; the plate is retained byone of the engine-to-transmission bolts, andby a second bolt securing the plate to the topof the transmission.36 Trace the wiring back from the sensor toits wiring connector, and disconnect it fromthe main wiring harness. Undo the retainingbolt, and remove the sensor from the top ofthe transmission housing.37 Refitting is a reversal of the removalprocedure, ensuring that the sensor wiring iscorrectly routed.

Fuel injection system relay unit38 The fuel injection system relay unit ismounted on the front of the enginecompartment junction box. To remove therelay unit, first disconnect the battery negativeterminal.39 Open up the junction box lid, then slackenand remove the relay mounting nut andwasher. Release the retaining clip, thendisconnect the wiring connector and removethe relay unit from the engine compartment(see illustrations).40 Refitting is the reverse of removal.

Note: Check parts availability with a Citroendealer prior to removing individualcomponents. At the time of writing, certaincomponents are only available as part of alarger assembly, eg the throttle switch is onlyavailable as part of the throttle housingassembly.

Fuel rail and injectors1 The fuel rail and injectors can be removedas described in Section 14, noting that it willfirst be necessary to remove the ignition HTcoil as described in Chapter 5.


14.39a Disconnect the wiringconnector...

Throttle switch3 Disconnect the battery negative terminal.4 Depress the retaining clip, and disconnectthe wiring connector from the throttlepotentiometer.5 Slacken and remove the two retainingscrews, then disengage the potentiometerfrom the throttle valve spindle and remove itfrom the vehicle.6 When refitting the switch, ensure it iscorrectly engaged with the throttle valvespindle, and lightly tighten its retainingscrews. Slowly operate the throttle valvewhilst listening to the switch; the switchshould click as soon as the throttle valvestarts to open, and again just before it is fullyclosed. Position the switch until this is so,then securely tighten its retaining screws.7 Reconnect the wiring connector, andreconnect the battery.

Electronic Control Unit (ECU)8 Refer to the information given in Section 14,noting that there is no idle mixture adjustmentpotentiometer to disconnect.

Airflow meter9 Disconnect the battery negative terminal.10 Depress the retaining clip, and disconnectthe wiring connector from the airflow meter.11 Slacken the retaining clips, anddisconnect the intake ducts from either end ofthe airflow meter.12 Slacken and remove the retaining nutsand bolts, and remove the airflow meter fromthe engine compartment.13 Refitting is a reverse of the removalprocedure.

Auxiliary air valve14 The auxiliary air valve is mounted on theleft-hand end of the cylinder head, directlybeneath the airflow meter.15 To improve access to the valve, removethe airflow meter as described above.16 Depress the retaining clip, and disconnectthe wiring connector from the air valve.17 Slacken the retaining clips, anddisconnect the vacuum hoses from either endof the auxiliary air valve.

14.39b . . . then undo the retaining bolt,and remove the fuel injection relay unit

from the front of the junction box

18 Undo the two retaining bolts, and removethe auxiliary air valve from the enginecompartment.19 Refitting is a reversal of the removalprocedure.

Manifold absolute pressure (MAP)sensor20 Refer to Section 14.


Intake air temperature sensor22 The intake air temperature sensor is anintegral part of the airflow meter, and is notavailable separately. Refer to paragraphs 9to 13 for airflow meter removal and refittingdetails.




Note: Check parts availability with a Citroendealer prior to removing individualcomponents. At the time of writing, certaincomponents are only available as part of alarger assembly, eg the throttle potentiometeris only available as part of the throttle housingassembly.

Fuel rail and injectorsNote: Refer to the warning note in Section 1before proceeding. If a faulty injector issuspected, before condemning the injector, itis worth trying the effect of one of theproprietary injector-cleaning treatments.1 Disconnect the battery negative terminal.2 Disconnect the vacuum pipe from the fuelpressure regulator.3 Bearing in mind the information given inSection 7, slacken the retaining clips, anddisconnect the fuel feed and return hoses

15 Bosch Motronic M1.3 systemcomponents -removal and refitting


16.8 Fuel pressure regulator location -1998 cc 16-valve models

from the right-hand end of the fuel rail. Wherethe original crimped-type Citroen hose clipsare still fitted, cut them off and discard them;use standard worm-drive hose clips onrefitting.4 Depress the retaining tangs, anddisconnect the wiring connectors from thefour injectors. To avoid the possibility of thewiring connectors being incorrectlyreconnected on refitting, mark eachconnector with its cylinder number (No 1 is atthe transmission end of the engine).5 Slacken and remove the two fuel railretaining bolts, then carefully ease the fuel railand injector assembly out from the inletmanifold, and remove it from the vehicle.Remove the O-rings from the end of eachinjector, and discard them; these must berenewed whenever they are disturbed.6 Slide out the retaining clip(s), and removethe relevant injector(s) from the fuel rail.Remove the upper O-ring from each injectoras it is removed, and discard it; all O-ringsmust be renewed once they have beendisturbed.7 Refitting is a reversal of the removalprocedure, noting the following points:(a) Fit new O-rings to all disturbed injectors.(b) Apply a smear of engine oil to the O-rings


(c) Using the marks made on removal, ensurethat all the injector wiring connectors arecorrectly reconnected.

(d) On completion, start the engine andcheck for fuel leaks.

Fuel pressure regulator8 Refer to Section 14 (see illustration).

Throttle potentiometer9 The throttle potentiometer is fitted to therear of the throttle housing.10 To improve access to the potentiometer,remove the throttle housing as described inSection 12.11 Undo the two retaining screws, andremove the potentiometer from the base ofthe throttle housing.

16.16 Disconnecting the wiring connectorfrom the idle speed auxiliary air valve -

1998 cc 16-valve models

12 On refitting, ensure that the potentiometeris correctly engaged with the throttle valvespindle, and securely tighten its retainingscrews.13 Refit the throttle housing as described inSection 12.

Electronic Control Unit (ECU)14 Refer to Section 17.

Idle speed auxiliary air valve15 The idle speed auxiliary air valve ismounted on the left-hand end of the inletmanifold, directly in front of the brakingsystem vacuum pump. To remove the valve,first disconnect the battery negative terminal.16 Depress the retaining clip, and disconnectthe wiring connector from the top of the valve(see illustration).17 Free the valve from its mounting rubber,then disconnect the two hoses from the baseof the valve and manoeuvre the valve out fromthe engine compartment.18 Refitting is a reverse of the removalsequence, ensuring that the hoses aresecurely reconnected.

Manifold absolute pressure (MAP)sensor19 The MAP sensor is an integral part of theelectronic control unit (ECU). Refer to Section17 for ECU removal and refitting details.


Intake air temperature sensor21 The intake air temperature sensor islocated in the throttle housing.22 To remove the sensor, first remove thethrottle potentiometer as described inparagraphs 9 to 11.23 Trace the wiring back from the sensor toits wiring connector, and remove the screwsecuring the connector to the top of thethrottle housing.24 Carefully ease the sensor out of position,and remove it from the throttle housing.Examine the sensor O-ring for signs ofdamage or deterioration, and renew ifnecessary.

16.27 Disconnecting the wiring connectorfrom the camshaft position sensor -


25 Refitting is a reversal of the removalprocedure, using a new O-ring wherenecessary. Refit the potentiometer asdescribed in paragraphs 12 and 13.

Camshaft position sensor26 The camshaft position sensor is locatedon the left-hand end of the cylinder head,directly over the end of the inlet camshaft. Toremove the sensor, first disconnect thebattery negative terminal.27 Depress the retaining clip, and disconnectthe wiring connector from the sensor (seeillustration).28 Undo the retaining screw, and withdrawthe sensor from the end of the cylinder head.Examine its O-ring for signs of damage ordeterioration, and renew if necessary.29 Refitting is a reversal of the removalprocedure, using a new O-ring wherenecessary.



Vehicle speed sensor32 The vehicle speed sensor is an integralpart of the transmission speedometer driveassembly. Refer to Chapter 7A for removaland refitting details.

Knock sensor33 The knock sensor is screwed onto therear face of the cylinder block.34 To gain access to the sensor, firmly applythe handbrake, then jack up the front of thevehicle and support it on axle stands. Accessto the sensor can then be gained fromunderneath the vehicle.35 Trace the wiring back from the sensor toits wiring connector, and disconnect it fromthe main loom.36 Slacken and remove the bolt securing thesensor to the cylinder block, and remove itfrom underneath the vehicle.37 Refitting is a reversal of the removalprocedure, ensuring that the sensor wiring is


17.5 Fuel feed hose connection (1),injector wiring connectors (2) and (two of

the three) fuel rail retaining bolts (3) -1998 cc 8-valve models

correctly routed and its retaining bolt securelytightened.

Throttle housing heating element38 The throttle housing heating element isfitted to the top of the throttle housing, and isan integral part of the throttle housing. At thetime of writing, no information is available onelement removal and refitting. Refer to yourCitroen dealer for further information.

Note: Check parts availability with a Citroendealer prior to removing individualcomponents. At the time of writing, certaincomponents are only available as part of alarger assembly, eg the throttle potentiometeris only available as part of the throttle housingassembly.

Fuel rail and injectorsNote: Refer to the warning note in Section 1before proceeding. If a faulty injector issuspected, before condemning the injector, itis worth trying the effect of one of theproprietary injector-cleaning treatments.1 Disconnect the battery negative terminal.2 Remove the air cleaner-to-throttle housingduct, using the information given in Section 2.3 Disconnect the vacuum pipe from the fuelpressure regulator.4 Release the retaining clip, and free thevarious hoses from the top of the fuel rail.5 Bearing in mind the information given inSection 7, slacken the retaining clip, anddisconnect the fuel feed and return hosesfrom the ends of the fuel rail. Where theoriginal crimped-type Citroen hose clips arestill fitted, cut them off and discard them; usestandard worm-drive hose clips on refitting(see illustration).6 Depress the retaining clips, and disconnectthe wiring connectors from the four injectors.7 Slacken and remove the three fuel railretaining bolts, then carefully ease the fuel railand injector assembly out from the inlet

17.16 Unclip the lid from the plastic box togain access to the ECU

manifold, and remove it from the vehicle.Remove the O-rings from the end of eachinjector, and discard them; these must berenewed whenever they are disturbed.8 Slide out the retaining clip(s), and removethe relevant injector(s) from the fuel rail.Remove the upper O-ring from each injectoras it is removed, and discard it; all O-ringsmust be renewed once they have beendisturbed.9 Refitting is a reversal of the removalprocedure, noting the following points:(a) Fit new O-rings to all disturbed injectors.(b) Apply a smear of engine oil to the O-rings


(c) On completion, start the engine andcheck for fuel leaks.


Throttle potentiometer11 Remove the throttle housing as describedin Section 12.12 Undo the two retaining screws, andremove the potentiometer from the base ofthe throttle housing.13 On refitting, ensure that the potentiometeris correctly engaged with the throttle valvespindle, and securely tighten its retainingscrews.14 Refit the throttle housing as described inSection 12.

Electronic control unit (ECU)15 The ECU is situated inside its ownprotective plastic box, located directly behindthe battery, on the left-hand side of the enginecompartment. To remove the ECU, firstdisconnect the battery negative terminal.16 Unclip the lid from the plastic box, andslide the ECU and mounting plate out ofposition (see illustration).17 Disconnect the wiring connector from theECU, then undo the retaining screws andremove the ECU from the enginecompartment.

17.21 Idle speed control stepper motor isretained by two screws (arrowed) - 1998 cc

8-valve models

18 Refitting is the reverse of removal,ensuring that the wiring connector is securelyreconnected.

Idle speed control stepper motor19 The idle speed control stepper motor islocated on the right-hand side of the throttlehousing assembly. To remove the motor, firstdisconnect the battery negative terminal.20 Release the retaining clip, and disconnectthe wiring connector from the motor.21 Slacken and remove the two retainingscrews, and withdraw the motor from thethrottle housing (see illustration).22 Refitting is a reversal of the removalprocedure.

Manifold absolute pressure (MAP)sensor23 The MAP sensor is situated on the right-hand side of the engine compartment,mounted on the front of theengine/transmission mounting (seeillustration). To remove the sensor, firstdisconnect the battery negative terminal.24 Undo the three retaining nuts, and free thesensor from the underside of the mountingbracket.25 Depress the retaining clip, disconnect thewiring connector and vacuum hose from thesensor, and remove the sensor from theengine compartment.26 Refitting is a reversal of the removalprocedure.

17.23 MAP sensor location - 1998 cc8-valve models

17 Magneti Marelli 8P.20 systemcomponents -removal and refitting


17.28 On 1998 cc 8-valve models, theintake air temperature sensor (arrowed) islocated in the base of the throttle housing


Intake air temperature sensor28 The intake air temperature sensor islocated in the base of the throttle housing(see illustration).29 To remove the sensor, first remove thethrottle housing as described in Section 12,then undo the two retaining screws andremove the throttle potentiometer from thebase of the housing.30 Trace the wiring back from the sensor toits wiring connector, and remove the screwsecuring the connector to the throttle housing.31 Carefully ease the sensor out of position,and remove it from the throttle housing.Examine the sensor O-ring for signs ofdamage or deterioration, and renew ifnecessary.32 Refitting is a reversal of the removalprocedure, using a new O-ring wherenecessary.



Throttle housing heating element35 The throttle housing heating element isfitted to the top of the throttle housing. Toremove the element, first disconnect thebattery negative terminal.36 Depress the retaining tangs, anddisconnect the wiring connector from theheating element, which is located on the right-hand side of the throttle housing cam (seeillustration).37 Undo the two screws securing the wiringconnector to the throttle housing, thendisplace the connector and carefully withdrawthe heating element from the throttle housing.Examine the element O-ring (where fitted) forsigns of damage or deterioration, and renew ifnecessary.38 Refitting is a reversal of the removalprocedure, taking great care to ensure that

17.36 Disconnecting the wiring connectorfrom the throttle housing heating element -


the element wiring does not become trappedas the wiring connector bolts are tightened.

Vehicle speed sensor39 The vehicle speed sensor is an integralpart of the transmission speedometer driveassembly. Refer to Chapter 7 A for removaland refitting details.

Knock sensor40 Refer to the information given in Sec-tion 16.

Removal1 Remove the throttle housing as describedin Section 12.

1761 cc models2 Undo the two bolts securing the wiring trayto the top of the manifold, and position thetray, and its associated wiring and hoses,clear of the manifold so that it does not hinderremoval.3 Depress the retaining clips, and disconnectthe wiring connectors from the four fuelinjectors.4 Bearing in mind the information given inSection 7, slacken the retaining clips, anddisconnect the fuel feed and return hoses

from the either side of the manifold. Where theoriginal crimped-type Citroen hose clips arestill fitted, cut them off and discard them; usestandard worm-drive hose clips on refitting.5 Slacken the retaining clip(s), anddisconnect the braking system vacuum servounit hose, and all the relevantvacuum/breather hoses, from the top of themanifold. Where necessary, make identi-fication marks on the hoses, to ensure theyare correctly reconnected on refitting.6 Undo the manifold retaining nuts, andwithdraw the manifold from the enginecompartment. Recover the two manifoldseals, and discard them - new ones must beused on refitting.

1905 cc models7 On models with a catalytic converter(Motronic M1.3 system), remove the ignitionHT coil as described in Chapter 5.8 Depress the retaining clips, and disconnectthe wiring connectors from the four fuelinjectors.9 Bearing in mind the information given inSection 7, slacken the retaining clips, anddisconnect the fuel feed and return hosesfrom the either end of the fuel rail. Where theoriginal crimped-type Citroen hose clips arestill fitted, cut them off and discard them; usestandard worm-drive hose clips on refitting.10 Slacken the retaining clip(s), anddisconnect the braking system vacuum servounit hose, and all the relevantvacuum/breather hoses, from the manifold(see illustration). Where necessary, makeidentification marks on the hoses, to ensurethey are correctly reconnected on refitting.11 Slacken or cut the retaining clip (asapplicable), and disconnect the breather hosefrom the top of the cylinder head cover.12 Slacken and remove the bolt securing thesupport stay to the underside of the manifold,and the bolt securing the oil filler/breatherneck to the left-hand side of the manifold (seeillustration).13 Undo the five manifold retaining nuts, andwithdraw the manifold from the enginecompartment. Recover the manifold gasket(s),and discard them - new gasket(s) must beused on refitting.

18.10 Disconnecting the braking systemvacuum servo unit hose from the manifold

-1905 cc models

18.12 On 1905 cc models, undo the bolt(arrowed) securing the oil filler/breather

neck to the manifold

18 Inlet manifold -removal and refitting


18.16 Removing the dipstick tuberetaining bolt - 1998 cc 8-valve models

1998 cc 8-valve models14 Carry out the operations described abovein paragraphs 8 to 10.15 Release the retaining clip, and free all thedisconnected hoses from the clip on the topof the fuel rail.16 Slacken and remove the bolt securing thedipstick tube to the side of the manifold (seeillustration).17 Undo the six nuts and bolts securing themanifold to the cylinder head, and remove themanifold from the engine compartment (seeillustration). Recover the manifold seals, anddiscard them - new ones must be used onrefitting.

1998 cc 16-valve models18 Slacken the retaining clip, and disconnectthe large breather hose from the front of theoil filler neck.19 Disconnect the vacuum/breather hosesfrom their unions on the front of the manifold,noting the location of each hose (seeillustration).20 Undo the three retaining screws, and liftoff the cover from the top of the inletmanifold-to-ACAV valve assembly joint. Freethe wiring loom, and position it clear of themanifold (see illustration).21 Slacken and remove the screws securingthe inlet manifold to the ACAV butterfly valvehousing, then manoeuvre the inlet manifoldout of the engine compartment. Recover the

18.17 Manifold retaining nut and boltlocations (arrowed) -1998 cc 8-valve

models

four intake tract sealing rings from themanifold, and discard them - new ones mustbe used on refitting.

Refitting22 Refitting is a reverse of the relevantremoval procedure, noting the followingpoints:(a) On 1905 cc models, ensure that the

manifold and cylinder head matingsurfaces are clean and dry, and fit newmanifold gasket(s) over the studs. Refitthe manifold, and tighten its retaining nutsto the specified torque.

(b) On 1761 cc and 1998 cc models, ensurethat the manifold and cylinder headmating surfaces are clean and dry, thenlocate the new seals in their recesses inthe manifold. Refit the manifold andtighten its retaining nuts and bolts (1761and 1998 cc 8-valve models) to thespecified torque; on 16-valve models,tighten the retaining screws securely.

(c) Ensure that all relevant hoses arereconnected to their original positions andare securely held (where necessary) bythe retaining clips.

(d) Refit the throttle housing as described inSection 12.

18.19 On 1998 cc 16-valve models, disconnectthe vacuum and breather hoses (arrowed)

from the front of the inlet manifold . . .

General information1 To ensure optimum efficiency at highengine speeds, and maximum torque at lowerengine speeds, 16-valve models have an inletmanifold with a variable intake tract system.Citroen call this system ACAV (variableacoustic characteristic induction) (seeillustration).2 The inlet manifold is divided into two tractsof different length and diameter; a long tract(for low-speed torque) which is 650 mm long,diameter 36 mm, and a short tract (for high-speed power) which is 370 mm long, diameter45 mm.3 Situated between the manifold and thecylinder head is a line of four butterfly valves,mounted in an alloy housing. Mounted oneither end of the housing is a vacuumdiaphragm assembly. Each diaphragm isconnected to the butterfly valve spindles via apushrod. The vacuum diaphragms areconnected to an electrically-operatedsolenoid valve, which is in turn connected tothe braking system vacuum pump. The pump

18.20 . . . then undo the three retainingscrews (arrowed) and remove the cover

from the top of the manifold

19.1 ACAV intakesystem -1998 cc16-valve models

1 Long inlet tract2 Short inlet tract3 ACAV butterfly

valves4 Vacuum

diaphragm unit5 Throttle cam6 Fuel injector

19 ACAV intake system(1998 cc 16-valve models) -general information, removaland refitting


is mounted on the end of the cylinder head,and is driven off the left-hand end of the inletcamshaft.4 At engine speeds below 1800 rpm andabove 5080 rpm, the ECU closes the solenoidvalve, shutting off the vacuum supply to thediaphragms, and the butterfly valves areclosed. With the valves closed, the shortintake tracts are closed, and the incoming airflows only through the long intake tract,boosting the torque output.5 At engine speeds between 1800 rpm and5080 rpm, the ECU opens the solenoid valve.The vacuum present in the pump is thenallowed to act on the vacuum diaphragms,which draws the pushrods into the diaphragmbodies, and opens up the four butterfly valves.With the valves open, the incoming air isallowed to flow through both the short andlong intake tracts, for maximum power.6 To check the system, start the engine andallow it to idle. Slowly increase the enginespeed, whilst observing the vacuumdiaphragm pushrods. At approximately 1800rpm, the pushrods should be drawn into thediaphragm bodies (valves open). Release thethrottle cam, and allow the engine to idleagain; the pushrods should extend from thediaphragms (valves closed).7 To check the operation of the solenoidvalve, disconnect the vacuum pipe from thediaphragm. Start the engine, and allow it toidle. Place your finger over the end of thepipe; no vacuum should be present in thepipe. Slowly increase the engine speed; atapproximately 1800 rpm, vacuum should befelt in the pipe. Allow the engine to idle again,and check that the vacuum supply is switchedoff. If this is not the case, either the solenoidvalve or its supply voltage is at fault.8 To check the operation of either vacuumdiaphragm assembly, disconnect the vacuumpipe, and suck hard at the control valve stub; thepushrod should be drawn into the diaphragmbody, and the valve should open. If this is notthe case, the vacuum diaphragm is faulty.

Removal and refittingACAV valve assembly9 Remove the inlet manifold as described inSection 18.10 Bearing in mind the information given inSection 7, slacken the retaining clip, anddisconnect the fuel feed and return hosesfrom their unions on the fuel rail. Where theoriginal crimped-type Citroen hose clips arestill fitted, cut them off and discard them; usestandard worm-drive hose clips on refitting.11 Depress the retaining tangs, anddisconnect the wiring connectors from thefour injectors. To avoid the possibility of thewiring connectors being incorrectlyreconnected on refitting, mark eachconnector with its relevant cylinder number(No 1 is at the transmission end of the engine).12 Disconnect the vacuum hoses from thefuel pressure regulator and the ACAVdiaphragm hose T-piece.

19.16 ACAV vacuum diaphragm unit -1998 cc 16-valve models

13 Slacken and remove the nuts and threebolts securing the valve assembly to thecylinder head, then slide the assembly off itsmounting studs and remove it from the enginecompartment. Remove the valve assemblygasket from the head, and discard it - a newone must be used on refitting.14 Examine the assembly, checking that thebutterfly valves open freely and closesmoothly. If not, the assembly must berenewed. The only components availableseparately are the vacuum diaphragm units -if either one is faulty, it must be renewed asdescribed below.15 Refitting is a reverse of the removalprocedure, noting the following points:(a) Ensure that the valve assembly and cylinder

head mating surfaces are clean and dry, andfit the new manifold gasket over the studs.Refit the valve assembly, and securelytighten its retaining nuts and bolts.

(b) Ensure all relevant hoses are reconnected totheir original positions, and are securely held(where necessary) by the retaining clips.

(c) Refit the inlet manifold as described inSection 18.

(d) On completion, check the operation of theACAV system as described above.

Vacuum diaphragm unit16 Disconnect the vacuum hose from thediaphragm unit. Using a suitable flat-bladedscrewdriver, carefully lever the unit pushrod offthe valve linkage balljoint (see illustration).17 Slacken and remove the two boltssecuring the diaphragm unit mounting bracketto the valve assembly, and remove thediaphragm from the engine.18 Refitting is a reversal of the removal

19.19 ACAV solenoid valve retainingnut (1), wiring connector (2) and hose

connections (3) -1998 cc 16-valve models

procedure, ensuring that the diaphragmpushrod is clipped firmly onto the linkageballjoint.

Solenoid valve19 The solenoid control valve is mounted onthe left-hand end of the cylinder head (seeillustration). To remove the valve, firstdisconnect the battery negative terminal.20 Depress the retaining clip, and disconnectthe wiring connector from the valve.21 Undo the nut securing the valve to thecylinder head, then withdraw the valve,disconnecting its vacuum hoses as theybecome accessible.22 Refitting is a reversal of the removalprocedure. Test the system on completion, asdescribed above.

20 Exhaust manifold -removal and refitting

Removal1 Firmly apply the handbrake, then jack upthe front of the vehicle and support it on axlestands.2 On 1905 cc models, to improve access tothe manifold from above, remove the aircleaner housing as described in Section 2,then undo the two mounting bracket retainingbolts, and remove the bracket from the top ofthe exhaust manifold (see illustrations).3 On all models, undo the bolts securing theshroud to the top of the manifold, and removethe shroud from the manifold (seeillustration).4 Slacken and remove the two nuts securingthe front pipe flange joint to the manifold, and

20.2a On 1905 cc models, undo the tworetaining bolts (arrowed)...

20.2b . . . and remove the air cleanermounting bracket from the top of exhaust

manifold


20.3 Undo the retaining bolts and removethe exhaust manifold shroud (1905 cc

model shown)

recover the springs. Remove the bolts, thenfree the front pipe from the manifold, andrecover the wire-mesh sealing ring. Eithersupport the front pipe, to avoid placing anystrain on the lambda sensor wiring (wherefitted), or disconnect the lambda sensorwiring connectors.5 Undo the retaining nuts securing themanifold to the head. Manoeuvre the manifoldout of the engine compartment, and discardthe manifold gasket(s) - new ones should beobtained for refitting.

Refitting6 Refitting is the reverse of the removalprocedure, noting the following points:(a) Examine all the exhaust manifold studs for

signs of damage and corrosion; removeall traces of corrosion, and repair orrenew any damaged studs.

(b) Ensure that the manifold and cylinder headsealing faces are clean and flat, and fit thenew manifold gaskets. Tighten the manifoldretaining nuts to the specified torque.

(c) Reconnect the front pipe to the manifold,using the information given in Section 21.

General information1 On 1905 cc models without a catalyticconverter, the exhaust system consists of twosections: the front pipe and intermediatesilencer box, and the tailpipe and mainsilencer box. The front pipe-to-manifold jointis of the spring-loaded ball type, to allow formovement in the exhaust system, and thefront pipe-to-silencer joint is secured by aclamping ring.2 On all other models, the exhaust systemconsists of three sections: the front pipe andcatalytic converter, the intermediate pipe andsilencer box, and the tailpipe and main silencerbox. All exhaust sections are joined by flangedjoints. The front pipe-to-manifold joint is of thespring-loaded ball type, to allow for movementin the exhaust system, and the front pipe-to-intermediate pipe and intermediate pipe-to-silencer joints are secured by clamping rings.

3 On all models, the system is suspended

21.6a Exhaust front pipe-to-manifold jointsecuring nut (1), spring cup (2) andspring (3) - viewed from underneath

throughout its entire length by rubber mountings.

Removal4 Each exhaust section can be removedindividually, or alternatively, the completesystem can be removed as a unit. Even if onlyone part of the system needs attention, it isoften easier to remove the whole system andseparate the sections on the bench.5 To remove the system or part of thesystem, first jack up the front or rear of thecar, and support it on axle stands.Alternatively, position the car over aninspection pit, or on car ramps.Front pipe -1905 cc models without acatalytic converter6 Slacken and remove the two nuts securingthe front pipe to the manifold, and recover thespring cups and springs. Remove the bolts,then release the front pipe from the manifold,and recover the wire-mesh gasket from thejoint (see illustrations).7 Slacken the front pipe-to-tailpipe clampingring bolt(s), and disengage the clamp from theflange joint.8 Free the front pipe from its mountingrubbers, and withdraw it from underneath thevehicle.Front pipe - all models with a catalyticconverter9 Trace the wiring back from the lambda(oxygen) sensor to its wiring connectors, anddisconnect it from the main wiring harness.10 Disconnect the front pipe from the manifoldand intermediate pipe as described above inparagraphs 6 and 7, then remove the front pipefrom underneath the vehicle. Be careful not todamage the catalytic converter - it is fragile.Intermediate pipe - all models with acatalytic converter11 Slacken the intermediate pipe clampingring bolts, and disengage the clamps fromboth the flange joints.12 Free the intermediate pipe from itsmounting rubbers, and withdraw it fromunderneath the vehicle.Tailpipe - all models13 Slacken the intermediate pipe-to-tailpipeclamping ring bolt(s), and disengage theclamp from the flange joint.14 Unhook the tailpipe from its mountingrubbers, and remove it from the vehicle.

21.6b Exhaust front pipe-to-manifold jointbolts (arrowed) - viewed from above

Complete system - all models15 Using the information given under therelevant sub-heading above, unbolt the frontpipe from the manifold, and disconnect thelambda sensor wiring (where applicable). Freethe system from all its mounting rubbers, andwithdraw it from under the vehicle.Heat shield(s) - all models16 The heat shields are secured to theunderside of the body by various nuts andbolts. Each shield can be removed once therelevant exhaust section has been removed. Ifthe shield is being removed to gain access to acomponent located behind it, it may provesufficient in some cases to remove the retainingnuts and/or bolts, and simply lower the shield,without disturbing the exhaust system.

Refitting17 Each section is refitted by a reverse of theremoval sequence, noting the following points:(a) Clamping rings which are secured by a

single bolt (fitted to all 1998 cc models,and to some others) should be renewedas a matter of course. They are designedto deform on tightening, and cannot bere-used.

(b) Ensure that all traces of corrosion havebeen removed from the flanges, andrenew all necessary gaskets.

(c) Inspect the rubber mountings for signs ofdamage or deterioration, and renew asnecessary.

(d) Prior to assembling the spring-loaded balltype joint, a smear of high-temperaturegrease should be applied to the jointmating surfaces. Citroen recommend theuse of Gripcott AF G2 grease (availablefrom your Citroen dealer).

(e) On joints which are secured by clampingrings, apply a smear of exhaust systemjointing paste to the joint mating surfaces,to ensure an gas-tight seal.

(f) Prior to tightening the exhaust systemfasteners, ensure all rubber mountings arecorrectly located, and that there isadequate clearance between the exhaustsystem and vehicle underbody.

(g) On models with clamping rings which aresecured by two bolts, tighten theclamping ring nuts evenly andprogressively to the specified torque, toensure that the clearance between theclamp halves is equal on either side.

21 Exhaust system -general information, removaland refitting

chapter 4 part c: fuel and exhaust systems - multi-point...

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