X5 Shaking, and Jerking forward

[hani831]

Hi guys,

I have a 2001 X5 3.0i with about 160K on it. I recently had my oil seperator replaced, and I am now having a problem where the car will be shaking when it is stopped at red light for example, and sometimes the rpm will dip down to 500rpm then jump back up to 700. When I let go of the brakes, the car keeps jerking forward and is not smooth at all. I find that this up until the car warms up, however the shaking on a stop is still there. My CEL is on, and when my mechanic scanned it he said it was the theromstat. Anyone ever have any issue like this or know what it could possibly be ?