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...

[v2rocket_aka944]

Hallooo
I would check the resistance of the Engine Coolant Temperature Sensor...
The one with the blue connector.
http://www.clarks-garage.com/pdf-manual/elect-19.pdf

DME Temperature Sensor Testing

Tools


Multimeter
Test Leads
Procedure


Turn the ignition switch OFF.
Disconnect the DME computer electrical connector.
Connect an ohmmeter between terminal 13 on the disconnected DME plug and ground.
Check for the following resistances:
DME Temperature Sensor Resistances
15-30 °C (59-86 °F)
At 59 °F approximately 3.3 k-ohms
At 86 °F approximately 1.46 k-ohms
NOTE
The next part of the DME temperature sensor testing assumes that the temperature gauge on the dash is working properly.

Connect the DME plug connector.
Start the car and run until the temperature gauge on the dash indicates approximately 80 °C (see dash temperature gauge section). If you suspect that the dash gauge is not working properly, you can check the surface temperature on the block near the DME temperature sensor.
Turn the engine OFF.
Disconnect the DME computer plug and connect ohmmeter as described in Step 3.
Turn the ignition switch back ON (Do Not Attempt to Start Car) and check dash indication is still reading 80 °C. Alternatively, check the surface temperature on the block near the DME temperature sensor. Compare resistance to the value in the table below.
DME Temperature Sensor Resistances
80 °C (176 °F)
280-360 ohms
If the resistances don't meet the tolerances listed, the DME Temperature sensor should be replaced. If the resistances indicate higher than the specs, it will cause a richer mixture. Lower resistances than the specs will result in a lean mixture.

[Noahs944]

Interesting. That is no fun.
This is a long shot, but might be the engine management computer (DME).
-is it possible water has leaked through onto the computer? One fellow had similar type of weird issues & it was a white layer of corrosion forming on the electrical pins/terminals on the dme where the connector attaches. Best of luck!