I have a 96 Audi A4. For some time now, the RPMs will dip (the car sometimes stalls) when idling. It is especially true when the car is cold (first stop light of the day) or in wet weather. I got the "can't reproduce the problem" response from my dealer.

My '97 2.8QM idle when stopped at a light would dip instantaneously to about 100 rpm then immedately back to normal 750. If this was an automatic it would have stalled. This may have happened once a day, sometimes more. I removed the Idle Air Control (IAC) valve and cleaned/lubricated it with WD40. This valve is completely different than the older Idle Stablization Valves found on 2.8L engines, but none the less requires the same amount of periodic cleaning. The valve is very hard to remove from the engine on my car with the A/C hoses directly in front of it. And the attachement nuts are also hard to get at. If you remove it, the plastic valve housing can be scrapped easily on the 3 threaded mounting studs and ruin the valve mounting mating surfaces!<p>I cleaned this valve 3 months ago and never experienced the rpm drop since then.

I've been having a similar problem on my 98 1.8T, complete with the check engine light. The dealer said they will have to change the ECU box, but they didn't have one and were going to get back to me. I still haven't heard from them a week later...<p>I seem to remember some other posts (last winter?) about this fix for rough idle/stalling/check engine light.

But the dealer told me to switch gas stations and I did for the most part as a new station had opened at about that same time. I haven't had the problem since then (that was about a year ago). The problem, BTW, lasted for about 2 months before it went away.

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