Questionhi there don,t know if you can advise, my p38 1998 deisel range rover, when driving up the gears only not down, every now and again the engine go,s in to idle mode/ stalls and the engine light comes on i have just spent 380.00 on the main injector in the engine as that was showing up on the diagnostic test as a fault but the fault is still there :-(
when it goes in to idle mode and the engine light comes on have to dip my clutch and rev and it corrects it self, hope U can help as no one seems to know whatis at fault
AnswerHi Joanne,
many years ago, I had my Disco into the dealer and they could not diagnose a rough idle and stalls (so they told me). After spending $5000 to fix what they thought was causing the trouble, I picked up the Disco and it stalled in the dealers parking lot. I was furious. Two weeks later, they said they had the fix - the TPS (throttle position sensor). Cost: $585.
Here's the techsheet info on your TPS:
Throttle Position Sensor (X171)
The DDE system is a ‘Drive by Wire’ system i.e. the throttle pedal does not directly control a throttle disc or the amount of fuel injected into the engine, but accelerator movements or ‘drivers request’ are sensed and the information is passed to the ECM (Z132). The ECM (Z132) calculates the maximum allowable fuel quantity from the air flow into the engine, engine speed, temperature, etc. It also includes information from strategies such as smoke limitation, active surge damping, automatic gear
change, fuel reduction, etc. to calculate the final figure. When driving, if the ‘drivers request’ signal is smaller than the maximum allowable quantity, then the requested quantity is injected. However, if the requested quantity is greater than the maximum allowable, then the latter quantity is injected rather than the driver’s demand. Therefore the Throttle Position Sensor (X171) is very important to the system.
It is located within the cab, close to the pedal assembly itself. The unit consists of a potentiometer and has three outputs:
1. Throttle Position – pin 37 ECM (Z132) The sensor outputs the pedal position to the ECM (Z132), which uses the information as described above.
2. Idle Position Switch – pin 25 ECM (Z132). The sensor has a separate idle position switch which informs the ECM (Z132) of the pedal status in the form of a simple on/off signal. This information is used by the ECM (Z132) to implement idle speedcontrol and other strategies i.e. overrun fuel shut–off.
3. Kick Down Switch. This switch is currently not used.
Another sensor to check:
Fuel Quantity Feedback Sensor
Located within the injection pump, this sensor sends the ECM (Z132) information regarding the actual quantity of fuel injected. Failure of the sensor or corrupted signals will illuminate the warning lamp and cause the engine to stall or not start. A second check, a plausibility check against the needle lift sensor, also takes place.
These two seem to be the most overlooked. I hope this helps.
Best of luck,
JohnMc
