Idling Troubles

[cinnabar_red]

I have a 5-speed 1986 325e that's been having some starting/idling issues.

When the engine is cold, I need to give it some throttle immediately after I start the car or it will stall. After a minute or so I can release the throttle and it will idle normally, at around 800 rpm. Sometimes, it will fluctuate between 200 and 800 rpm until it evens out. When I shift into neutral, occasionally the rpms will drop to about 300 and bounce up and down once or twice until it normalizes. It sounds like it is going to stall but very rarely does. The battery light comes on for a second when it does this.

So far, I have cleaned the ICV and replaced the fuel temp sensor. Neither seemed to make a difference. I've been living with this problem for a while now but I'd love to get it worked out. Any advice would be much appreciated :)

[turbo55]

Fuel temp sensor? You mean coolant temp sensor probably? The one on the thermostat housing (with all the thick coolant lines going in/out of it?) I doubt a bad temp sensor would make that significant of an impact.
How did you clean the ICV? Does the little shutter inside move pretty freely?
I'd check for vacuum leaks first. Rubber boot (check all around), vacuum hoses, ICV connections, as well as the charcoal canister purge line going into the bottom of the throttle body could leak. Also could be the intake manifold gaskets, although a leak as large as to stall an engine would probably be one of the other things. Don't forget that purge line, mine was almost ripped off!
There are multiple ways you can check for vacuum leaks: listen for hissing, use a cigar, use a propane torch, or do a smoke test. A visual inspection should find obvious ones.

Your battery light going on is just a result of the very low rpms when you're near stall. The voltage regulator can't compensate for the low engine speed so the alternator output voltage drops off, which causes the light to go on.

[exhaust]

+1 for vacuum leaks. Unless you've changed the intake boots and vacuum lines while you've owned it, they're probably dead or on their way out.

[cinnabar_red]

Sorry, meant coolant temp sensor.

I have replaced the intake boot recently, but I will check the vacuum lines.

Thanks for all the info!

[packratbimmer]

There is also an idle switch on the thermostat housing that can affect idle on an eta car (not there on the i car).


It is a two prong switch - not sure how to test it - probably simple on/off deal