1991 535i (e34) Idle Stumbles - BMW Forum

erubin · 03-28-2005, 10:01 PM

Idle is poor. Sounds like stumble or miss.

Checked/replaced or cleaned ignition sysem. New OE plugs.
Cleaned the idle control valve.
Checked for vacuum leaks.
Measured and compared with spec the throttle position switch and idle control valve.
Did not service the fuel injectors as i don't know how to identify which one(s) may be bad.

The only thing I found is that the idle control valve goes to completly closed when ignition switch turned on (engine not running). My Alldata info says it should open to 50%. Could this be a problem. But how could the engine even run at all with the ICV completly closed. I have a feeling that the valve does not remain completly closed when running. I don't believe the ICV opening can be checked with the engine running.

The engine is not hunting just stumbling at idle. Any suggestions?

omega112 · 03-29-2005, 01:15 PM

I have been having the same issue with my 90 535i. I havent checked the ICV though. I do need a valve adjustment, and replacement of the Thermostat. Both are supposed to help Idle problems. One thing that helped was some Injector Cleaner. I used Redline S1 Injector cleaner and it made the idle much better. It doesnt seem to miss as much anymore. It is still off though.