vacilating idle, unintended acceleration '99 528I

I have a new problem with my car. Ever since it started getting cold again, I have a problem with a vacillating idle. It only lasts for minute or 2 while the engine is warming up. The engine starts fine when cold but goes into this vacillating mode after a minute or two. After the engine warms up it idles fine. I initially thought it was related to vacuum leaks since I was getting intermittent CEL's and vacuum related codes. I found and fixed the vacuum leaks and now have no codes or CEL's. This idle problem did not go away.



I seems like the idle starts to drop (600 RPM to under 500) and the engine tried to compensate rapidly and I get a small burst of acceleration. If I only have my foot lightly on the brake the acceleration can overcome the brakes and I get a small lurch forward. This is not a good thing.



I would like to fix this if anyone knows what it could be.



Thanks



Rich

vacilating idle, unintended acceleration '99 528I