Idle Speed Question 2
09-10-2001, 05:34 PM
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Idle Speed Question 2
As I stated on my last note my S2 is idling at about 1250 - 1300 rpm when hot. I believe this can be caused by the Aux Air Valve not closing when the engine is hot. Does anyone know which sensors provide the signal to the DME for control of this valve and how to test them / the valve?
Skip - I had a look but don't think there are any air leaks.
Keith
944S2
Skip - I had a look but don't think there are any air leaks.
Keith
944S2
09-10-2001, 08:23 PM
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Sounds like you're on the right track, though not sure from here 
The idle stabilizer rcvs commands from the DME directly... the input to the DME for the operation of this valve are from the TPS (in a closed position) and the O2 sensor (air/fuel mixture). If the mixture at idle (with throttle closed) is too rich, the DME will open the Idle Stabilizer to allow more air. The RPM is set by the DME to be near 840 or 900 (depends on model)... it's the job of the DME to regulate the injectors and idle stabilizer to ensure proper idle. The RPM is read at the flywheel. So, you have many possibilities for failure, just when referring to idle. Real fun, isn't it.
The Idle Stabilizer can in some cases be cleaned (carbon buildup leads to failure) and reinstalled with varied success. You could try unpluggin the idle stabilizer (electrically) to see what happens... but, I tend to believe your diagnosis is correct, and the Idle Stabilizer is faulty.
Good Luck!
The idle stabilizer rcvs commands from the DME directly... the input to the DME for the operation of this valve are from the TPS (in a closed position) and the O2 sensor (air/fuel mixture). If the mixture at idle (with throttle closed) is too rich, the DME will open the Idle Stabilizer to allow more air. The RPM is set by the DME to be near 840 or 900 (depends on model)... it's the job of the DME to regulate the injectors and idle stabilizer to ensure proper idle. The RPM is read at the flywheel. So, you have many possibilities for failure, just when referring to idle. Real fun, isn't it.
The Idle Stabilizer can in some cases be cleaned (carbon buildup leads to failure) and reinstalled with varied success. You could try unpluggin the idle stabilizer (electrically) to see what happens... but, I tend to believe your diagnosis is correct, and the Idle Stabilizer is faulty.
Good Luck!