When To Replace A Fuel Injector Brought to you by AASADuring its evolution, the fuel injector has moved from the intake manifold to the combustion chamber. This has made them more precise in dispensing fuel. If this precision is thrown off by restrictions, electrical problems or fuel problems, it can cause driveability issues.Here are 10 signs to look for when you need to replace a fuel injector or it needs service.

1. RestrictionsA restriction of only 8% to 10% in a single fuel injector can lean out the fuel mixture and cause a misfire. When this occurs, unburned oxygen enters the exhaust and makes the O2 sensor read lean. On older multiport systems that fire the injectors simultaneously, the computer compensates by increasing the on time of all the injectors, which can create an overly rich fuel condition in the other cylinders.Direct fuel injectors are more sensitive to restrictions because of the precise amount of fuel they inject into the combustion chamber.2. Turbo TroublesIn turbocharged engines, dirty injectors can have a dangerous leaning effect that may lead to engine-damaging detonation. When the engine is under boost and at a higher rpm, it needs all the fuel the injectors can deliver. If the injectors are dirty and cant keep up with the engines demands, the fuel mixture will lean out, causing detonation to occur. The leaning out may cause higher than normal exhaust temperatures and turbo failure.3. Heat SoakWhen the engine is shut off, the injectors undergo heat soak. Fuel residue evaporates in the injector nozzles, leaving the waxy olefins behind. Because the engine is off, there is no cooling airflow moving through the ports and no fuel flowing through the injectors to wash it away, so heat bakes the olefins into hard varnish deposits. Over time, these deposits can build up and clog the injectors. Even if a vehicle has low mileage, short drive cycles and increased heat soaks can clog the injector.Since the formation of these deposits is a normal consequence of engine operation, detergents are added to gasoline to help keep the injectors clean. But if a vehicle is used primarily for short-trip driving, the deposits may build up faster than the detergents can wash them away. On four-cylinder engines, the No. 2 and No. 3 injectors are in the hottest location and tend to clog up faster than the end injectors on cylinders No. 1 and No. 4. The same applies to the injectors in the middle cylinders in six- and eight-cylinder engines. The hotter the location, the more vulnerable the injector is to clogging from heat soaks. Throttle body injectors are less vulnerable to heat soak because of their location high above the intake manifold plenum.Heat soak can affect direct-injection injectors due to their placement in the head. Even with the higher pressures, the orifices can become clogged over time.

4. Increase or Decrease in Long- and Short-Term Fuel TrimsThe fuel calibration curves in the Powertrain Control Module (PCM) are based on OEM dyno testing using a new engine. Fuel pressure is within a specified range for that engine, and the injectors are all clean and new. The PCMs built-in adaptive fuel control strategies allow it to adjust both short-term and long-term fuel trim to compensate for variances in fuel pressure and fuel delivery to maintain the correct air/fuel ratio but only within certain limits.The PCM may not be able to increase injector duration enough to offset the difference if: An injector becomes clogged with fuel varnish deposits and fails to deliver its normal dose of fuel when its energized, or Fuel pressure to the injector drops below specifications because of a weak fuel pump, plugged fuel filter or leaky fuel pressure regulator.This can leave the air/fuel mixture too lean, causing the cylinder to misfire.

5. Not Enough ResistanceThe solenoid at the top of the injector creates a magnetic field that pulls up the injector pintle when the injector is energized. The magnetic field must be strong enough to overcome the spring pressure and fuel pressure above the pintle, otherwise the injector may not open all the way. Shorts, opens or excessive resistance in the injector solenoid can also cause problems.Typically, the solenoids often short internally when injectors fail, which causes a drop in resistance. If the specification calls for 3 ohms, for example, and an injector measures only 1 ohm, it will pull more current than the other injectors. Too much current flow to an injector may cause the PCM injector driver circuit to shut down, killing any other injectors that also share that same driver circuit. One way to check the injectors is with an ohmmeter.6. Longer Crank TimesAn injector leak will cause the rail to lose pressure while the vehicle is sitting resulting in a longer than normal crank because the rail will need extra time to pressurize.

A normal crank time in a diesel common-rail injection system is usually around three to five seconds. This is how long it will take the common-rail pump to build fuel pressure to the threshold. The fuel rail pressure threshold for cranking occurs around 5,000 psi. Normal common-rail systems will operate at 5,000 psi at idle and can reach up to 30,000 psi at wide open throttle.7. Failed Balance TestsIf you suspect that an injector is clogged or malfunctioning, an injector balance test can isolate the bad injector. Scan tools that can disable injectors can isolate an injector for diagnostics. Engine rpm drop may not be an effective diagnostic method when performing a cylinder balance test where an injector is disabled.

A more effective method is looking at the voltage changes from the O2 sensor. Leaking injectors and some dead injectors can be missed even when an injector is disabled. Other problems with the ignition system and mechanical components also may not show an rpm loss when an injector is turned off. If an injector is good, the voltage from the O2 sensor will drop to or below 100mV. If the problem is a closed or dead injector, the long-term fuel trim may have compensated enough so that the voltage doesnt change.Another effective test is to measure the pressure loss in the fuel rail when each injector is fired and pulses for a set period of time. Use an electronic injector pulse tester for this. As each injector is energized, a fuel pressure gauge is observed to monitor the drop in fuel pressure. The electrical connectors to the other injectors are removed, isolating the injector being tested. The difference between the maximum and minimum reading is the pressure drop.Ideally, each injector should drop the same amount when opened. A variation of 1.5 to 2 psi or more is cause for concern. No pressure drop, or a very low pressure drop, is a sign the orifice or tip is restricted. A higher than normal pressure drop indicates a rich condition that could be caused by a stuck plunger or worn pintle.8. Misfire CodesA lean misfire may trigger a misfire code and turn on the check engine light. The code often will be a P0300 random misfire code, or you may find one or more misfire codes for individual cylinders, depending on which injectors are most affected.

9. Vehicle Wont Start With Full TankMajor symptoms of contaminated fuel can include cranking no-start, hard starting, stalling, loss of power and poor fuel economy. Because symptoms of fuel contamination generally appear immediately after refueling, the fuel gauge needle pegged on full should always be a diagnostic red flag. Remember to ask if the vehicle has recently been refueled because some drivers just add fuel rather than topping off their tanks.10. Lack of MaintenanceIf an owner has neglected maintenance services like oil changes and filter replacements, chances are the fuel injectors will suffer. For port fuel applications, not changing the oil can result in blowby and a compromised PCV system, which builds up contaminates on the tip of the injector. Not changing the oil in an engine with direct fuel injection can result in a worn fuel pump camshaft lobe.Engine Air Temperature SensorCopyright AA1Car

The Intake Air Temperature sensor (IAT) monitors the temperature of the air entering the engine. The engine computer (PCM) needs this information to estimate air density so it can balance air air/fuel mixture. Colder air is more dense than hot air, so cold air requires more fuel to maintain the same air/fuel ratio. The PCM changes the air/fuel ratio by changing the length (on time) of the injector pulses.On pre-OBD II vehicles (1995 & older), this sensor may be called an Air Charge Temperature (ACT) sensor, a Vane Air Temperature (VAT) sensor, a Manifold Charging Temperature (MCT) sensor, a Manifold Air Temperature (MAT) sensor or a Charge Temperature Sensor (CTS).HOW THE AIR TEMPERATURE SENSOR WORKSThe Intake Air Temperature sensor is usually mounted in the intake manifold so the tip will be exposed to air entering the engine. On engines that use mass airflow (MAF) sensors to monitor the volume of air entering the engine, the MAP sensor will also have an air temperature sensor built into it. Some engines may also have more than one air temperature sensor (two if it has a split intake manifold or separate intake manifolds on a V6 or V8 engine).

The air temperature sensor is a thermistor, which means its electrical resistance changes in response to changes in temperature.It works the same as a coolant sensor. The PCM applies a reference voltage to the sensor (usually 5 volts), then looks at the voltage signal it receives back to calculate air temperature. The return voltage signal will change in proportion to changes in air temperature. Most air temperature sensors are negative temperature coefficient (NTC) thermistors with high electrical resistance when they are cold, but the resistance drops as they heat up. However, some work in the opposite manner. They are positive temperature coefficient (PTC) thermistors that have low resistance when cold, and increase in resistance as they heat up. The changing resistance of the sensor causes a change in the return voltage back to the PCM.On older pre-OBD II applications (1995 & older vehicles), the signal from the air temperature sensor may also be used to turn on the cold start injector (if used) if the outside air temperature is cold. On some of these older applications, the air temperature sensor signal may also be used to delay the opening of the EGR valve until the engine warms up.Air temperature sensors are also used in Automatic Climate Control systems. One or more air temperature sensors are used to monitor the temperature of the air inside the passenger compartment, as well as the outside air temperature. The climate control system usually has its own separate outside air temperature sensor located outside the engine compartment so engine heat does not affect it. The outside air temperature sensor will usually be mounted behind the grille or in the cowl area at the base of the windshield.). Most of these sensors work exactly the same as the engine air temperature sensor. But some use an infrared sensor to monitor the body temperature of the vehicles occupants.CAUSES OF FAILUREAn air temperature sensor can sometimes be damaged bybackfiring in the intake manifold. Carbon and oil contamination inside the intake manifold can also coat the tip of the sensor, making it less responsive to sudden changes in air temperature. The air temperature sensor itself may also degrade as a result of heat or old age, causing it to respond more slowly or not at all.Sensor problems can also be caused by poor electrical connections at the sensor. A loose or corroded wiring connector can affect the sensors output, as can damaged wiring in the circuit between the sensor and PCM. DRIVEABILITY SYMPTOMSIf the intake air temperature sensor is not reading accurately, the PCM may think the air is warmer or colder than it actually is, causing it to miscalculate the air/fuel mixture. The result may be a lean or rich fuel mixture that causes driveability symptoms such as poor idle quality when cold, stumble on cold acceleration, and surging when the engine is warm. If the engine computer uses the air temperature sensor input to turn on a cold start injector, and the sensor is not reading accurately, it may prevent the cold start injector from working causing a hard cold start condition. A faulty air temperature sensor may also affect the operation of the EGR valve is the PCM uses air temperature to determine when the EGR valve opens (on most, it uses the coolant temperature input). On OBD II application (1996 & newer vehicles), a faulty air temperature sensor may prevent the Evaporative (EVAP) Emissions System Monitor from completing. This can prevent a vehicle from passing a plug-in OBD II test (because all the OBD II monitors must run before it can pass the test). The EVAP monitor will only run when the outside temperature is within a certain range (not too cold and not too hot, as a rule).A faulty air temperature sensor that is reading warmer than normal will typically cause in a lean fuel condition. This increases the risk of detonation and lean misfire (which hurts fuel economy and increases emissions).A faulty air temperature sensor that is reading colder than normal will typically cause a rich fuel condition. This wastes fuel and also increases emissions.Sometimes what appears to be a fuel mixture balance problemdue to a faulty air temperature sensor is actually due tosomething else, like an engine vacuum leak or even a restricted catalytic converter! A severe exhaust restriction will reduce intake vacuum and airflow causing the sensor to read hotter than normal (because it is picking up heat from the engine). DIAGNOSING THE AIR TEMPERATURE SENSORA faulty air temperature sensor may or may not set a code and turn on the Check Engine light. If the sensor circuit is open or shorted, it will usually set a code. But if it is only reading high or low, or is sluggish due to old age or contamination, it usually will not set a code.A quick way to check the air temperature sensor is to use a scan tool to compare the air temperature reading to the coolant temperature reading once the engine is warm. A good air temperature sensor will usually read a few degrees coolerthan the coolant sensor.The sensor's resistance can also be checked with an ohmmeter. Remove the sensor, then connect the two leads on the ohmmeter to the two pins in or on the sensors wiring connector plug to measure the sensors resistance. Measure the sensors resistance when it is cold. Then blowhot air at the tip of the sensor with a blow drier (never use a propane torch!) and measure the resistance again. Look for a change in the resistance reading as the sensor warms up. No change in the sensors resistance reading as it heats up would tell you the sensor is bad and needs to be replaced. The sensor reading should gradually decrease if the sensor is a negative thermistor, or gradully increase if it is a positive thermistor. If the reading suddenly goes open (infinite resistance) or shorts out (little or no resistance), you have a bad sensor.To be really accurate, you should look up the resistance specifications for the air temperature sensor, then measure the sensors resistance at low, mid-range and high temperatures to see if it matches the specifications. A sensor that reads within the specified range when cold, may go out of range at higher temperature, or vice versa. Such a sensor would not be accurate and should be replaced. The resistance and/or voltage test specifications for the air temperature sensor on your engine can be found in a service manual, or by subscribing to the service information on the (Vehicle Mfrs Service Information Website or AlldataDIY. REPLACEMENT/REPAIR/ADJUSTMENTThe air temperature sensor is a solid state device so no adjustment is possible. However, it may be possible to clean a dirty sensor so that it functions normally once again provided it is still in good working condition. Contaminants can be removed from the tip of the sensor by (1) removing the sensor from the intake manifold, then (2) spraying the sensor tip with electronics cleaner. For sensors that are mounted inside a MAF sensor, the wire sensing element can also be sprayed with aerosol electronics cleaner. Do not use any other type of cleaner as it may damage the plastic housing or leave behind a chemical residue that may cause problems down the road.If a sensor is not reading within specifications or has failed, replace it. Fortunately, most air temperature are not very expensive (typically less than $30). Dealers always charge more than aftermarket auto parts stores, so shop around and compare prices before you buy. Labor to change an air temperature sensor is usually minimal, unless the sensor is buried under a lot of other stuff that has to be removed.When replacing the air temperature sensor, be careful not to overtighten it as this may damage the sensor housing, or the threads in a plastic intake manifold.Exhaust Gas Recirculation (EGR)Copyright AA1CarThe Exhaust Gas Recirculation (EGR) system's purpose is to reduce NOx emissions that contribute to air pollution. The first EGR systems were added to engines in 1973, and today most engines have an EGR system.As long as the EGR system is functioning properly, it should have no noticeable effect on engine performance. But if the EGR system is leaking or inoperative, it can cause driveability problems, including detonation (knocking or pinging when accelerating or under load), a rough idle, stalling, hard starting, elevated NOx emissions and even elevated hydrocarbon (HC) emissions in the exhaust.WHY EGR?Exhaust gas recirculation reduces the formation of NOX by allowing a small amount of exhaust gas to "leak" into the intake manifold. The amount of gas leaked into the intake manifold is only about 6 to 10% of the total, but it's enough to dilute the air/fuel mixture just enough to have a "cooling effect" on combustion temperatures. This keeps combustion temperatures below 1500 degrees C (2800 degrees F) to reduce the reaction between nitrogen and oxygen that forms NOx.

HOW EGR WORKSTo recirculate exhaust back into the intake manifold, a small calibrated "leak" or passageway is created between the intake and exhaust manifolds. Intake vacuum in the intake manifold sucks exhaust back into the engine. But the amount of recirculation has to be closely controlled otherwise it can have the same effect on idle quality, engine performance and driveability as a huge vacuum leak. Most older EGR systems use a vacuum regulated EGR valve while newer vehicles tend to have an electronic EGR valve to control exhaust gas recirculation. When the engine is idling, the EGR valve is closed and there is no EGR flow into the manifold. The EGR valve remains closed until the engine is warm and is operating under load. As the load increases and combustion temperatures start to rise, the EGR valve opens and starts to leak exhaust back into the intake manifold. This has a quenching effect that lowers combustion temperatures and reduces the formation of NOx.In addition to EGR, other methods may also be used to minimize NOx. These include increasing camshaft valve overlap, redesigning the combustion chamber and modifying ignition advance curves. Three-way catalytic converters also reduce NOx in the exhaust. Some engines run so clean that they do not need an EGR system to meet NOx emission standards.If the EGR system is rendered inoperative because it was disconnected or tampered with, the cooling effect that was formerly provided by the EGR system will be lost. Without EGR, the engine will often knock and ping (detonate) when accelerating or lugging the engine. This can cause engine damage over time.TYPES OF EGR VALVESThere are six different types of EGR valves:

Ported EGR valves (1973 to 1980s). The typical ported vacuum EGR valve consists of a vacuum diaphragm connected to a poppet or tapered stem flow control valve. The EGR valve itself is usually mounted either on a spacer under the carburetor or on the intake manifold. A small pipe from the exhaust manifold or an internal crossover passage in the cylinder head and intake manifold routes exhaust to the valve. When vacuum is applied to the EGR valve, it opens. This allows intake vacuum to suck exhaust into the engine. To prevent the EGR valve from opening when the engine is cold, the vacuum line to the EGR valve may be connected to a parted vacuum switch or a computer-controlled solenoid. Vacuum is not allowed to pass to the valve until the engine is warm. EGR isn't needed when the engine is cold, only when it is warm and under load.Positive backpressure EGR valves (1973 & up). Backpressure EGR valves use exhaust backpressure to vary the point at which they open and their flow rates. On GM cars, they are identified by the last letter on the part number on top of the valve. A letter "P" indicates a positive backpressure valve, and a letter "N" indicates a negative backpressure valve. Inside a backpressure EGR valve is a second diaphragm that reacts to backpressure in the exhaust system. The backpressure diaphragm opens and closes a small bleed hole in the main EGR vacuum circuit or diaphragm chamber. Opening the bleed hole reduces vacuum to the main diaphragm and prevents the valve from opening fully. Closing the bleed hole allows full vacuum to reach the main diaphragm so the valve can open wide and allow maximum EGR flow. With positive backpressure EGR valves, any increase in exhaust backpressure causes the EGR valve to open. This reduces backpressure somewhat, allowing the backpressure diaphragm to bleed off some control vacuum. The EGR valve begins to close and exhaust pressure rises again. The EGR valve oscillates open and closed with changing exhaust pressure to maintain a sort of balanced flow.Negative backpressure EGR valves (1973 & up). The negative backpressure type of EGR valve reacts in the same way, except that it reacts to negative or decreasing pressure changes in the exhaust system to regulate EGR action. A drop in backpressure occurs when there is less load on the engine. This causes the backpressure diaphragm to open a bleed hole and reduce EGR flow. It's the same principle as with the positive type except that the control function occurs when backpressure goes down instead of up. NOTE: Most precomputer EGR systems have a temperature vacuum switch(TVS) or ported vacuum switch between the EGR valve and vacuum source to prevent EGR operation until the engine has had a chance to warm up. The engine must be relatively warm before it can handle EGR. If an engine runs rough or stumbles when cold, it may indicate a defective TVS that is allowing EGR too soon after starting. A TVS stuck in the closed position would block vacuum to the EGR and prevent any EGR operation. The symptom here would be excessive NOx emissions and possible pinging or detonation. Pulse-width modulated electronic EGR valves (early 1980s & up). First used in 1984 by General Motors, this type of EGR system uses a pulse width-modulated EGR control solenoid. With this technique, the powertrain control module (PCM) cycles the EGR vacuum control solenoid rapidly on and off. This creates a variable vacuum signal that can regulate EGR operation very closely. The amount of "on" time versus "off" time for the EGR solenoid ranges from 0 to 100 percent, and the average amount of "on" time versus "off" time at any given instant determines how much EGR flow occurs.Digital electronic EGR valves (late 1980s to 1990s). On some applications, a "digital" EGR valve is used. This type of valve also uses vacuum to open the valve but regulates EGR flow according to computer control. The digital EGR valve has three metering orifices that are opened and closed by solenoids. By opening various combinations of these three solenoids, different flow rates can be achieved to match EGR to the engine's requirements. The solenoids are normally closed, and open only when the computer completes the ground to each.

Linear electronic EGR valves (early 1990s & up). Another type of electronic EGR valve is the "linear" EGR valve. This type uses a small computer-controlled stepper motor to open and close the EGR valve instead of vacuum. The advantage of this approach is that the EGR valve operates totally independent of engine vacuum. It is electrically operated and can be opened in various increments depending on what the engine control module determines the engine needs at any given moment in time. GM started using this type of valve on many of its engines in 1992. Linear EGR valves may also be equipped with an EGR valve position sensor (EVP) to keep the computer informed about what the EGR valve is doing. The EVP sensor also helps with self-diagnostics because the computer looks for an indication of movement from the sensor when the it commands the EGR valve to open or close. The sensor works like a throttle position sensor and changes resistance. The voltage signal typically varies from 0.3 (closed) to 5 volts (open).

APPLICATIONS WITH NO EGR VALVEOn many late model engines with Variable Valve Timing(VVT), there is no EGR valve because the VVT system varies the timing of the exhaust valves to provide the same effect as EGR. By changing the point at which the exhaust valves close when the engine is working hard under load, a small amount of exhaust gas can be retained in the cylinders for the next combustion cycle. This has the same effect on reducing combustion temperatures and NOx as recirculating exhaust gas from an exhaust port back into the intake manifold through an EGR valve. The big difference is that the VVT system can react to changing engine loads much more quickly and precisely than a traditional EGR valve. Using VVT for EGR also eliminates many of the problems associated with EGR valves such as carbon buildup and valve sticking or failure.COMMON EGR PROBLEMSPinging (spark knock or detonation) because the EGR system is not working, the exhaust port is plugged up with carbon, or the EGR valve has been disabled.Rough idle or misfiring because the EGR valve is not closing and is leaking exhaust into the intake manifold. You may also find a P0300 random misfire code on OBD II vehicles.Hard starting because the EGR valve is not closing and is creating a vacuum leak into the intake manifold.EGR DIAGNOSTICSFind out what kind of EGR valve is on the vehicle so you can use the appropriate test procedure. Examine the valve or refer to a service manual. On some vehicles, you may find this information on the underhood emissions decal. Also, find out what kind of vacuum controls are used in the vacuum plumbing. Does it have a ported vacuum switch or a solenoid? Follow the vacuum connections from the valve, refer to a service manual or the underhood emissions decal for vacuum hose routing information.There are several ways to troubleshoot an EGR system. You can follow the EGR troubleshooting procedure that's listed in a service manual for the engine. On late model computer controlled engines, there may be trouble codes that relate to the EGR system. On such an application, the first step would be to read out the code or codes using a scan tool or code reader. You would then refer to the specific diagnostic charts in a service manual that tell you what to do next.EGR Trouble Codes:P0400....Exhaust Gas Recirculation FlowP0401....Exhaust Gas Recirculation Flow Insufficient DetectedP0402....Exhaust Gas Recirculation Flow Excessive DetectedP0403....Exhaust Gas Recirculation Control CircuitP0404....Exhaust Gas Recirculation Control Circuit Range/PerformanceP0405....Exhaust Gas Recirculation Sensor 'A' Circuit LowP0406....Exhaust Gas Recirculation Sensor 'A' Circuit HighP0407....Exhaust Gas Recirculation Sensor 'B' Circuit LowP0408....Exhaust Gas Recirculation Sensor 'B' Circuit HighP0409....Exhaust Gas Recirculation Sensor 'A' CircuitOn pre-OBD II GM applications, a code 32 indicates an EGR problem. The logic by which the onboard diagnostics detects trouble follows one of two routes. On some applications, a code 32 is set when the computer detects a richer fuel mixture off idle (indicating no EGR). On others, a code is set if the computer energizes the EGR vacuum solenoid but does not detect a corresponding drop in intake vacuum. On pre-OBD II Fords, a code 31 indicates a problem with the EGR valve position sensor (EVP). It works like a throttle position sensor, going from high resistance (5500 ohms) when the EGR valve is closed to low resistance (100 ohms) when it is open. You'll find these EVP sensors mostly on Ford EEC-IV V6 and V8 engines. Other codes include a code 32 which indicates the EGR circuit is not controlling. A code 33 is triggered when the EVP sensor is not closing, and a code 34 indicates no EGR flow. Any of these codes could indicate a faulty EGR valve as well as a problem in the EGRC or EGRV vacuum solenoids. Other codes include a code 83 (EGRC circuit fault) and code 84 (EGRV circuit fault). Both indicate an electrical problem in one of the solenoid circuits. The solenoids should have between 30 and 70 ohms resistance. See Emission Guide for emissions testing and diagnosis information. Emission Guide is a quick reference program that covers basic emission controls and emissions testing.FORD EGR PROBLEMSOn 1995 and newer vehicles with OBD II, P0400 to P0409 codes indicate various faults in the EGR system.

Click to see larger image of Ford DPFE sensorA common EGR problem with many Fords is a bad DPFE (differential pressure) sensor. The DPFE sensor is part of the EGR system and senses EGR flow when the EGR valve is open. It provides a feedback signal to the engine computer so it can vary EGR flow to meet changing engine loads. The DPFE sensor is usually mounted on the engine and is connected to the pipe that runs from the exhaust manifold to the EGR valve with two rubber hoses. When the sensor goes bad, the Check Engine light comes on and typically sets any or all of teh following fault codes: P0171 & P0174 (lean codes), and/or P0401 (insufficient EGR flow). Nine out of ten times, the fault is not a bad EGR valve or a vacuum leak, but a bad DPFE sensor. A replacement costs about $112 at Ford, or about $48 at an aftermarket auto parts store.

EGR TROUBLESHOOTING PROCEDUREThe following "generic" procedure can help you troubleshoot EGR problems.1. Does the engine have a detonation (spark knock) problem when accelerating under load? Refer to the timing specs for the engine and check ignition timing. The timing may be overadvanced. If the timing is within specs, check the engine's operating temperature. A cooling problem may be causing the engine to detonate. If the temperature is within its normal range and there are no apparent cooling problems, other possibilities to investigate include a spark plugs that are too hot for the engine application, a lean air/fuel mixture, low octane fuel or too much compression (due to a buildup of carbon in the combustion chambers or because of pistons or heads that have too much compression for the fuel you're using). Be sure you've ruled out all the other possibilities before focusing on the EGR system.2. Use a vacuum gauge to check the EGR valve vacuum supply hose for vacuum at 2000-2500 rpm. There should be vacuum if the engine is at normal operating temperature. No vacuum would indicate a problem such as a loose or misrouted hose, a blocked or inoperative ported vacuum switch or solenoid, or a faulty vacuum amplifier (or vacuum pump in the case of a diesel engine).Sometimes loss of EGR can be caused by a failed vacuum solenoid in the EGR's vacuum supply line. Refer to a vacuum hose routing diagram in a service manual or the hose routing information on the vehicle's emission decal for the location of the solenoid. If the solenoid fails to open when energized, jams shut or open, or fails to function because of a corroded electrical connection, loose wire, bad ground, or other electrical problem, it will obviously affect the operation of the EGR valve. Depending on the nature of the problem, the engine may have no EGR, EGR all the time, or insufficient EGR. If bypassing the suspicious solenoid with a section of vacuum tubing causes the EGR valve to operate, find out why the solenoid isn't responding before you replace it. The problem may be nothing more than a loose or corroded wiring connector.3. Inspect the EGR valve itself. Because of the valve's location, it may be difficult to see whether or not the valve stem moves when the engine is revved to 1500 to 2000 rpm by slowing opening and closing the throttle. The EGR valve stem should move if the valve is functioning correctly. A hand mirror may make it easier to watch the valve stem. Be careful not to touch the valve because it will be hot! If the valve stem doesn't move when the engine is revved (and the valve is receiving vacuum), there's probably something wrong with the EGR valve.Another way to "test" the EGR valve on some engines is to apply vacuum directly to the EGR valve. Note; This only works on ported vacuum EGR valves, not backpressure EGR valves or electronic EGR valves. Vacuum should pull the valve open creating the equivalent of a large vacuum leak. This should cause a momentary drop in idle speed and a noticeable increase in idle roughness.Backpressure type EGR valves are more difficult to check because there must be sufficient backpressure in the exhaust before the valve will open when vacuum is applied. One trick that's sometimes used is to create an artificial restriction by inserting a large socket into the tailpipe, then applying vacuum to the valve to see if it opens. Don't forget to remove the restriction afterwards.4. Remove and inspect the EGR valve if you suspect a problem. Most failures are caused by a rupture or leak in the valve diaphragm. If the valve is not a backpressure type, it should hold vacuum when vacuum is applied with a hand-help pump. If it can't hold vacuum, it needs to be replaced. Note: This test does not work on backpressure EGR valves.Backpressure EGR valves sometimes fail if the hollow valve stem becomes clogged with carbon or debris. This you can see for yourself. It's almost impossible to remove such a clog, so replace the EGR valve.Carbon accumulation around the base of the EGR valve can sometimes interfere with the opening or closing of the valve. These can be removed by careful brushing or by soaking the tip of the valve in solvent. Do not soak the entire valve in solvent or allow solvent to get anywhere near the diaphragm. The solvent will attack and ruin the diaphragm.5. Inspect the EGR passageway in the manifold for clogging. Use a pipe cleaner or small piece of wire to explore the opening for a blockage. Sometimes you can dislodge material that's clogging the opening by carefully poking at it. Other times, it may be necessary to remove the manifold and have it professionally cleaned. Also recommended is to clean the throttle body and intake manifold at the same time to remove varnish and carbon deposits.

HOW TO REPLACE EGR VALVEWith so many variations from one vehicle application to the next in emission control systems and calibration, it is extremely important that you get the correct replacement EGR valve for the application. Two EGR valves may look identical but be calibrated differently in terms of flow and the amount of vacuum and/or backpressure it takes to open the valve. Therefore, you may have to refer to the vehicle's VIN number as well as year, make, model and engine size when ordering a replacement EGR valve. It may also be necessary to refer to the OEM part number on the old EGR valve (if possible) when ordering a replacement, so don't throw the old EGR valve away until you have the new one, have installed it and made sure it's working correctly.Many aftermarket EGR valves are "consolidated" so fewer part numbers are necessary to cover a wider range of vehicle applications. Some of these valves use interchangeable restricters to alter their flow characteristics. Follow the suppliers instructions as to which restricter to use for the correct calibration.

EGR Valve Service & CleaningThe following video is courtesy of Wells Manufacturing via YouTube1. R1200GSA pinging, knocking, pre-ignition, detonation, stall To- Candyman and Marki GSA, I totally agree with you both.I have a 2008 R12000GS with 28k fully serviced by dealer (latest only 2 weeks ago) and it still exhibits the same traites as you describe Candyman.I have a GS 911 (purchased in a desparate attempt to solve the pinging/popping on decceleration) and although I have used it to observe stuff it's so far never got me tinkering with things except idle actuator calibration but after reading the post with the GS911 graphs included and Marki GSA's post that may change.I also am suffering from the stall issue.I commute on my bike and when dealing with urban start/stop stuff I need to blip when dropping clutch in 2nd making ready for 1st or it will likely stall and as Candyman says- it's bloody dangerous not mentioning embarassing, frustrating, annoying etc. You have to get it into neutral and start it on the button and if the lights have just turned green....well, all bikers can imagine.I've been through the all too common situation with the BMW dealer- they couldn't see any fault on the computer, they replaced coils, said they all pop/bang to some extent etc etc and with the dealer being 40miles away I can't keep returning to insist on further action but I think they either don't care or don't know.So here I am on my 2nd GS that I dearly love but these issues are becoming too much to take (so much so, I test drove the Triumph Tiger Explorer but it did't quite float my boat)I just want my GS fixed!As Marki GSA says- "it shouldn't do this"Any advice appreciated. P2096 Post Catalyst Fuel Trim System Too Lean Bank 1OBD-II Trouble Code Technical DescriptionArticle by

Don BowmanASE Certified Automotive TechPost Catalyst Fuel Trim System Too Lean Bank 1What does that mean?This is a generic powertrain code, which means it covers all makes/models, 1996-newer. However, specific troubleshooting steps will vary depending on the vehicle.The code P2096, post catalyst fuel trim system too lean on bank 1 simply translates to a lean (too much air and not enough fuel) condition the PCM recognized through the signals from the oxygen sensors. Bank 1 has no meaning on a four or straight six cylinder engine with a single exhaust. On a V-6 or V-8 engine it refers to the oxygen sensor on the number one cylinder side of the engine as bank 1.A series of oxygen sensors in the exhaust system signal the fuel mixture ratio at all times. Each exhaust system with a catalytic converter will have two sensors -- one between the engine and the converter and one after the converter. Oxygen sensors signal the engine management computer the amount of oxygen present in the exhaust, which is used in determining and controlling the fuel ratio. The higher the oxygen content the leaner the fuel mixture, conversely the opposite is a rich mixture. It does so in a series of pulses called "cross counts." There is zirconium on the tip of the sensor that reacts to oxygen in a way that when hot, creates its own voltage. It must be around 250 degrees F to operate and will produce up to 0.8 volts. In operation the oxygen sensor will cycle once every second and send a voltage to the computer that ranges from 0.2 rich to 0.8 for a rich mixture. The perfect mixture will average the signals around 0.45 volts. The computer's target fuel/air ratio is 14.7:1. An oxygen sensor will not function at low temperatures such as start up -- for this reason most forward sensors have a pre-heater to reduce their warm up time.The mission of the oxygen sensors are twofold -- to indicate the unburned oxygen in the exhaust and secondly, to indicate the proficiency of the catalytic converter. The engine-side sensor signals the mixture entering the converter and the rear sensor signals the mixture exiting the converter. When the sensors and converter are operating properly, the front sensor will have a higher count than the rear sensor indicating a functioning converter. When the front and rear sensor agree, the front oxygen sensor has failed, the converter is plugged or another component is causing the oxygen sensor to give an erroneous signal.This code may and may not be noticeable less for the check engine light. It depends on the cause, however, there isn't anything that can fail on a vehicle without adversely effecting something else. Trace the problem to correct the code as soon as possible to avoid damage to any other components.SymptomsThe symptoms of a P2096 code will vary depending on the component or system causing the disruption in the fuel trim. Not all will be present simultaneously. Malfunction Indicator Lamp (MIL) illumination with P2096 DTC set Rough idle Poor fuel economy Poor acceleration Misfire Cherry red hot catalytic converter Possible spark knock (detonation / pre-ignition) Additional codes associated with the P2096Potential CausesThe causes for this DTC may include: Low fuel pressure caused by a clogged filter, failing fuel pump, failed fuel pressure regulator or clogged or leaking injectors. Rough running engine due to misfiring plugs. Many engines have misfire codes to indicate the cylinder effected, such as P0304 for number 4. A large vacuum leak would cause a massive amount of un-metered air to enter the intake manifold resulting in an overly lean mixture. A large air leak at or near the number one oxygen sensor would also cause a lean mixture. A plugged converter will cause of host of driveability problems as well as set this code. A severely plugged converter will result in the inability to increase rpm when under load. Look for a code such as P0420 -- catalytic converter efficiency below threshold if the converter indicating a faulty converter. A faulty oxygen sensor. This will set a code in itself, however, a faulty oxygen sensor does not automatically condemn the sensor. The code just means that the sensor signal was not within specifications. An air leak or any of the above will cause an erroneous signal. There is a multitude of O2 codes relating to O2 performance which gives a clue to the problematic area. The Mass Airflow sensor will also cause this problem. It would be accompanied by a code such as P0100 -- Mass Airflow circuit malfunction. The Mass Airflow sensor is a hot wire that senses the volume of air entering the intake manifold. The computer uses this information to control fuel mixture. Rusty exhaust systems, cracked exhaust manifolds or damaged or missing gaskets or donuts will cause air leaks. To make a point as to the cause and effect on vehicles, consider this scenario. A simple air leak forward of the number one oxygen sensor will add additional air to the mixture un-metered by the computer. The oxygen sensor signals a lean mixture due to the un-metered air. Immediately the computer enriches the mixture to prevent a lean mixture from causing damage due to detonation among other factors. The unnecessarily rich mixture begins to foul the plugs, contaminate the oil, heats up the converter and drops the fuel economy. These are only a few of the things that transpire under these circumstances.Diagnostic and Repair ProceduresIt's wise to go online and acquire the technical service bulletins (TSBs) associated with these codes and a description. Although all vehicles suffer from similar causes, some may have a service history of problems with a particular component associated with this code.If you have access to an advanced diagnostic scan tool such as a Tech II or Snap-On Vantage, this will save you a lot of time. The scanner has the ability to graph and display digital information in real-time of each sensor's performance. It will show the oxygen sensors in operation to easily recognize one that is malfunctioning.Jeeps and some Chrysler products seem to suffer from poor electrical connectors, so inspect them thoroughly. Additionally, Jeeps have had several PCM updates on the later models. The reprogramming of the updates as well as oxygen sensor replacement for any reason is covered under the 8 year / 80,000 mile warranty. To check if the update has been completed, look next or behind the battery and there will be a serial number with the date of updating the computer. If it hasn't been done it is free for the above period. Connect the code scanner to the OBD port under the dash. Turn the key to "On" with the engine off. Depress the "Read" button and the codes display. Cross-reference any additional codes with the accompanying code sheet. Direct your attention to these codes first. In lieu of additional codes corresponding to code P2096 or P2098 test drive the vehicle and look for tell-tale symptoms. Fuel contamination will cause this code. Fill up with a higher grade. If the vehicle displays very little power and difficulty in accelerating, look underneath the vehicle with the engine running. A clogged converter will normally glow red. Check the engine for vacuum leaks between the Mass Airflow sensor and the intake manifold. Many times leaks sound like a whistle. Repair any leaks and clear the code. If the engine displays a miss and there wasn't a code, determine which cylinder is misfiring. If the exhaust manifold is visible, spay or pour a small amount of water on each cylinder exhaust port. Water will evaporate immediately on good cylinders and slowly on the missing cylinder. If this can't be accomplished pull the plugs and check the condition. Look at the plug wires to make sure they are not burnt or laying on the exhaust. Inspect the exhaust system. Look for rust holes, missing gaskets, cracks or looseness. Raise the vehicle and with a 7/8 inch wrench, make sure the oxygen sensor is tight. Inspect the wiring harness and connector. If a code for the Mass Airflow sensor displays check its connector. If it is alright replace the MAF sensor. Replace the forward oxygen sensor on the side of the engine with the number -1 cylinder for code P2096. Also, if a oxygen sensor code stating "heater circuit malfunction" the sensor has most probably failed.Register now to ask a question (free) Related P2096 DTC Discussions 2010 mazda cx7 2.3l p2096need help my 2010 mazda cx7 2.3l has 3 codes all are the same p2096 i took to a shop they told me i needed an upstream o2 sensor so i change it cleared the code the next day lite back on don't know what to do tried of throwing away money.... 2002 VW Passat 2.8L, P2096 codeI'm getting an intermittent, (about once a week), P2096 code--"Fuel trim Bank1 too lean". So far it has happened only about say 10 minutes after starting the car and at speeds less than 30 MPH and with low RPMs--between 1350 and 1550. 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I have tried everything I can find and I even stumped my local dealership.....Need more help with a p2096 code?If you still need help regarding the P2096 trouble code, please post your question in our FREE car repair forums.