Porsche 944 S2 idle problem

[Bruno2414]

Hello,

the car starts perfect when it's cold and runs perfect at idle .
When I want to restart the car immediately when he is hot, no problem. When I wait a half hour it will not start at the first attempt but immidiately at the second attempt.
The problem starts when the engine is really hot. You come to a red light and after 20 or 30 seconds on idle the engine stops running, when I hear it and I am fast with the throttle I can safe it and hold him running at 1100 à 1200 refs. If the car stopped running you can restart him with full throttle or wait some time to let him cool a little bit. Then he runs like nothing happend.
When it's really bad and you are going to a long downhill with a tiny bit of throttle of no throttle at all you hear a few explosions in the exhaust and the engine stops running.
I allready changed the DME-relay, replaced the Bosch idle valve, tested the idle switch... no result.

Anyone had the same problem?

I'm dutch speaking, so sorry for the bad spelling...

[E-bmw]

Due to the bit you say about running downhill with no throttle I would be looking at checking throttle position sensor (I am assuming you don't have a throttle stop/cut out) as with no throttle on there should be no fuel going in so you shouldn't be getting pops/bangs.

Is it possible that this could also give your other issues?

Yes it is possible.

[GreenV8S]

I assume the hot start problem is that the engine cranks over but won't fire. That might be heat soak in the fuel rail. You might find that just keying on an off a couple of times (does the pump prime on key-on in that car?) will flush enough fuel through to clear the problem.

The fact you can prevent the hot engine stall by opening the throttle suggests it might be a fueling problem. I don't know whether that car has a flood clear mode when you crank with full throttle, but if it does then your symptoms seem to suggest it's over fueling at hot idle. That might be a tuning problem or a sensor problem (coolant temp sensor, fuel temp sensor, throttle position sensor, lambda sensor could all affect the fueling).

[Bruno2414]

I can see it on the rev's when it will happen. Normally he does 1000 revs on idle. Then he slowly goes to 800 revs and the oil pressure goes down. It the past, the car corrected on his own to 1100 revs for a few seconds and went back to 1000 revs and continued on idle. But now, after a while at 800 rev's, he dies very very very slowly... with a little bit of shaking at the end.
It's a convertible, I can also smell him dying at the last meters before the red light.