Looking for an answer. My 6 cylinder gas Bimmer has had an intermittent drivability problem for about 10 years. When happening, the car does not hold the 'idle gas' as I will call it. Everytime I take my foot off the gas, the car will quit. I'm doing 55 mph, take my foot off the gas and it quits. As long as I keep my foot on the gas, AOK.
Vacuum leak or idle control valve perhaps? What happens when you first start the car; does it idle properly? Does it stall when the engine's cold or hot? What year is your car? If it's a newer E30, then it won't have the idle control valve (I think it's electronically controlled).
My 325 (no letters) was built in late 1986 and is an 1987 model. Most of the time the car drives fine. But, when the problem occurs it is on initial start-up and usually irons-out over 5 or 10 minutes. One time, in the rain, the problem persisted for an hour and 50 miles of travel. Recently, it showed up on a nice hot day after sitting for several days. That lasted for about 10 minutes.
Oh, yeah. When the problem is occurring I must keep my foot on the gas to keep the car running. So, yeah, the car immediately stalls out after firing up. It does start, though.
You probably have a bad idle valve or idle control module. Adjust it according to the repair manual or take it to someone that can. If the valve cannot be adjusted to repair the problem, you must replace both the valve and the module (the "green box") or do away with the system.
I was going to post that but rethought it. If his engine dies immediately after lifting off the throttle at highway speeds (in gear), then I have a hard time believing it has anything to do with an idle module. Problem is, it does it when cold as well, which actually does point to the idle control. He definitely has an idle control valve; we both share the same production time period (late 1986) and we've goth got eta's. What is this green box you speak of? Where is it located? I've replaced my valve but still have problems, though they're different than what he is stating.
Green box is located above the ECU. I would also suspect a vacuum leak for him, but for this to have been ongoing for 10 years, without getting worse, I lean toward idle control system.
