Yet another idle post....

Ok I have read everything I possibly can find relating to idle issues and I'm stumped. Here's the situation...

The odd idle occurs only when cold and when the car is first started. Idle runs up to about 2500 rpms and will drop back to the 2000 range and then oscillate between 1800 and 2k until it warms up. The idle will only seem to oscillate when the clutch is let out and the car is put in neutral (or after coming to a stop after driving before it is warmed up). Once the car hits normal opperating temperature it idles perfect.

Here is what has been done:

1) Throttle body has been cleaned thoroughly.
2) BISS has new 0-ring
3) ISC checks out fine
4) Disabled the egr valve (pulled the vacuum lines and capped them)
5) Can't find any vacuum leaks.

One other point of interest. Even after the car is warm I can reproduce the surge by backing out the idle screw so that it idles at 1500ish.

I'm really running out of ideas at this point so any suggestions are appreciated.

Thanks in advance for the help,

Gary

The car is a 1991 Talon Tsi FWD. Forgot to mention that in the first post.

Damn! Another one! Mine is doing the same thing. I don't have much time to troubleshoot, though. It's happening to the early 1G's... Maybe it's an ECU Y2K issue? (:

Is your car misfiring? Running rich? Poor fuel economy? If you have an aftermarket boost gauge, what's the vacuum reading at idle? (Mine's 10in/hg.)

Try ECU caps if you didn't do them yet..
Also check your wastegate actuator to see if it s not keeping the flapper open by any chance.. that's one vacuum leak that took me a while to detect..

I don't have a boost gauge hooked up to it yet so I'm not sure of the actual vacuum reading. The car is basically bone stock except for a k&n with an opened up air box. The car runs rich during the cycling stage but great once it's warmed up. I'm getting good gas mileage as well.

Could this idle phenomenom be the result of a bad gasket around the intake mani? When it warms up the leak reseals? Just thinking out loud here so bare with me. I have also heard of problems with the ISC (or IAC) in other cars... like Hyundai's, where the internals actually corode over time and result in unhindered air flow through the ISC. Since this seems to be an elusive prob, and seems to be happening on the older DSM's, I just thought that I would throw some thoughts out there for all to consider.
A.

you mentioned that you turned the idle down to 1500-ish when the car is warm and it surges...Thats exactly what is supposed to happen. The ecu is stepping the ISC up and down in its search for 750 RPM's.

Try grounding the timing connector and grounding terminal #10 of the diagnostic connector and check your idle. It should be 750. do all this with the engine warmed up.

If it aint close to 750, adjust your throttle cable, biss screw, but dont touch the TPS (its factory set).

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Len...
92 Talon TSi AWD
89 2000 GTX