1997 BMW E36 – Falling Idle – Stalling – M50, M52
This answer is applicable for many BMWs in addition to the one listed below.
I have a 1997 BMW 328I. I have taken it to the shop 3 times for idling problems. They have replaced hoses for compression and other things and still when the car is cold it won’t stay idle. When I stop at a stop sign or red light it will shut off. The rpm hand drops below zero and the car will shut off. When leaving work I have to sit in the car with foot on accelerator until car warms up, about 5 minutes. Even when I go into a store the few minutes I am away I have to repeat this process. This is very annoying and embarrassing when I have passengers to not be able to get into the car and leave. My BMW has never been cold natured, no matter what the weather temperature I have always been able to start the car and leave it to warm up by itself.
We would suggest three general areas in relation to your idle problems.
* Vacuum leaks – ALL hoses that carry air, including; intake, idle control and crankcase ventilation, as well as the fuel vent system, charcoal canister, etc …… must be checked for cracks and loose fittings.
* Idle control valve – The idle control valve may be inoperative. This valve continuously opens and closes to keep the idle at the specified point. The valve may be stuck and not keeping the idle up. The valve is located under the intake manifold.
* Engine temperature sensor – The engine temp sensor may be faulty and not telling the engine management system what the proper engine temp is. This is less likely, due to the fact that you noted the problem can occur both cold and hot. With an automatic transmission, you can perform a little test of the idle control circuit. Assuming you can get the engine to idle, in PARK, check the RPM on the tachometer. Now, place the transmission into DRIVE. Does the RPM drop? If so, this is an indicator that the idle control valve may be faulty. We do keep these (and all of the other parts) in stock. Let us know what you find, or feel free to call our agents at 800-535-2002.
Bentley Repair Manual:
Idle Control Valve:
Engine temperature sensor: