I have a strange hot start issue with my 944S2. If I start the car from cold it starts and runs ok throughout warm-up. The idle can be a bit lumpy at times, and it seems to be running a bit rich when warm, but it will run and drive.
If I start the car when it's hot, it will start fairly easily (cranks over a little longer than when cold), and will idle but quite roughly, and you can smell it's running really rich. When I then try to rev it, the revs will rise briefly but then start to bog down and the revs will gradually drop until it stalls, usually accompanied by some pops and bangs. If I release the throttle when it starts to bog down it will go back to rough idle. When doing this I can smell it's running incredibly rich.
So it seems like when I do a hot start, the car is fuelling as if it were a cold start. It's as if switching the engine off causes the engine to lose all it's temperature readings. The only way I've found to drive it after a hot start is basically to let it idle for about 10 minutes without revving it, and then it seems to lean out enough that it will drive reasonably normally again.
I have two DME relays, so I've tried swapping between them, but it makes little difference to the problem. I've also replaced the coolant temperature sensor near the front of the crankcase with a new Bosch one, and that didn't make any difference either. There's a temperature sensor in the underside of the intake manifold which I have a spare used one of from my old engine so I'm going to try swapping that over to see if it makes any difference. However I cannot find any mention of that temp sensor in the PET diagrams, and there is no part number displayed on the sensor itself.
So I have 2 questions:
- what is the Porsche part number for the temp sensor in the intake manifold / does it appear anywhere in the PET diagrams?
- what else could be causing it to over-fuel so much after hot start?
Sorry for the essay!
