Idle control valve
I have a '96 328 but I did check the BMW TIS CD for a '92 325i and it described your condition as a faulty or dirty Idle speed control valve. It says the original ICV was replaced with a newer version because of problems and the part # is 13 41 433 626 This new ICV requires a different air hose P/N 13 41 1 730 071 but mentioned the hose may come with the ICV when ordered new. I believe you will find a hose about 3/4" diameter coming off the bottom of the air intake pipe elbow just before the throttle body. This hose will lead down under the intake manifold where the ICV is located. The BMW TIS CD show the full proceedure of removing testing and replacing the ICV. I have read tons of threads on the ICV and some claim you can clean them, I removed the throttle body from my car and the air pipe from the bottom of the ICV then shot a bunch of FI safe throttle body cleaner through it; lots of carbon did come out but my car still starts a little rough. From all the threads I have read on this, most people just live with it. My rough start is only about 2-3 seconds long, but I have found that a quick pump of the gas as the car starts avoids the condition. As I mentioned before, The BMW TIS mentioned that the ICV from your year has been replaced, so you may find resolve in replacing yours. Good luck, hope I was helpful.
