I have a 1981 320i that I've had for some time now. Starts great, runs well, but have one issue in the cold weather I'm looking for some input on. When I first got the car, it would not stay running and had poor idle at start up. I removed the WUR and cleaned out the screen. Fixed the starting issue. Once winter hit (I live where it's currently -30 F and hasn't been above freezing for a month) the car still starts just fine and runs well for the first approx 2 minutes. Then the idle will surge between 300-1200 rpm and while driving will usually die at a stop. However, this surge in idle and dying at a stop only lasts 5 minutes or so before engine is warmed up and idles smoothly at around 900-1000rpm.
The car has recently replaced fuel filter, spark plugs, dist cap, and oxygen sensor (had same issue before they were replaced).
I have not been able to locate any vacuum leaks.
I am guessing the problem is auxiliary air slide valve, but wanted to check on this forum first. The aux air valve is clean inside and the valve opens and closes in the cold and heat, but I do not know how to test it beyond that.
Any suggestions?
I'm going to take a wild guess and say your WUR is not sufficiently enriching the mixture when cold. It IS adjustable.
I'd suggest (if possible) that you invest in a fuel pressure gauge setup and check the system pressure, and cold and hot control pressures..
Last edited by cgifool; 03-05-2019 at 10:58 AM.
If you wipe the inside of the tail pipe just after it's warmed-up (with finger, rag, whatever), does it come out clean, or lots of soot, or just a little soot?
Do the same after driving it around the block a few times too.
Tbd
Hi ...
There is an additional cold running enrichment system on the Lambda controller on the North American models. It's controlled by a temperature switch screwed into the back of the engine lifting bracket on the front left of the engine. It should be closed below 17 oC. Or maybe the connectors on the switch may have a bad contact causing an intermittent connection causing the lambda controller to cycle the extra enrichment.
About the only tests you can do on the AAV is as you have all ready done .. seeing if it opens and closes ... and you can test the heating coil for resistance. Mine comes in at a bit over 50 Ω and others here have said theirs were up about 60 Ω. Again it would be worth checking the electrical contacts in the plug and socket on the AAV, mine where pretty grotty when I got my E21.
Cheers
hmm .. Wonder what happens if I do this ...
It has very little soot after just warming up, no soot after its driven around for a while.
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I'll take a look at this switch - that's something I have not noticed.
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Now that the weather has warmed up to a balmy freezing or just above freezing, the engine is running fine and no hesitation or stalling issues. Seems that when the temperature outside was anywhere from 0 to -30 F. the car had that problem. Now even though it's still around 20 degrees in the morning, it starts fine, rpms are a little higher for the first few minutes of running, then back to normal. No dip in rpms at stopping. Took it for a good long drive on the interstate this past Sunday and ran great.
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