Any help with this, 2005 Cayenne (non S)? Symptoms:

- Hard starting on first attempt. It sometimes dies after starting, but on a second attempt it is fine. The engine grumbles for 20-30 seconds, but then is OK.

- Every once in a while, it gives a PSM error.

From the Durametric:

- P1538: Throttle adjusting unit (lower mechanical stop) relearning - Implausible signal, test conditions are not-completed, fault is not currently active and not causing a DTC light.
- P2714: Throttle/Pedal Position Sensor/Switch E Circuit - Implausible signal, test conditions are not-completed, fault is not currently active and not causing a DTC light.

- P0300: Random/Multiple Cylinder Misfire Detected - Implausible signal, test conditions are not-completed, fault is not currently active and causing a DTC light.
- P0301-P0306: Cylinder 1-6 Misfire Detected - Implausible signal, test conditions are not-completed, fault is not currently active and causing a DTC light.

 

Random misfire codes can have many causes , but a lean fuel condition is the most common . A combination of random misfire codes and throttle related codes in my opinion point to a fuel supply issue. I would check fuel pumps as this may also explain hard starting. One basic check is to listen for the primary fuel pump when you open the drivers door.

 

Thanks, I will have a look. What should I be listening for? I remember having an issue a while back (300ZX) where the check valve (I think) was dying. So it wouldn't keep the fuel pressurized.

I guess what you are listening for is the fuel pump pressurizing before you start the car? It would make sense that if that system is not working right (either not pressurizing/priming or back check valve) that the car would hard start.

I reset the codes and it surprising has mostly gone away. I have still had an issue with it stuttering within the first couple minutes in the morning. I would think it should have been primed by then, but maybe it is just fuel pressure in general. I am not sure if there is an easy place to hook up a fuel pressure gage though?

 

You would normally hear a buzz for about 2 seconds when you open the drivers door. This is just a very basic check, because there could still be an issue even if you can hear something.


I've attached a few pages from the repair manual on the full fuel pressure test.

PORSCHE CAYENNE Fuel Pressure Test 2003-2006.pdf