3-Series (E21, E30)Chat relating to the BMW 3-Series from 1975-1983 and 1984-1991 line. Specific models: BMW 315, BMW 316, BMW 318, BMW 318i, BMW 320/4, BMW 320i, BMW 320/6, BMW 323i, BMW 320i. E30 Family models include: BMW 325e, BMW 325i, BMW 325is, BMW 325ix.
Ok, I may have asked this before, but I'm at my wits end.
Car was idling high (around 1100-1200) decided that maybe the ICV was dirty. Pulled it off and cleaned a bunch of crud out, and reinstalled. Now the car will idle up to about 1500 then drop down to around 800 then back up again.
I've attempted to set the idle with the screw on the ICV and found that the faster I set the idle, the faster it cycles up and down.
I've sprayed carb cleaner over every hose I can find, as well as the intake manifold, and can find no vacuum leaks. My only other thought was the O2 sensor, but would that cause a regularly pulsing idle? Do I need a new ICV? I've set the idle screw all the way down to the stop, and it still seems to be idling high.
I read your instructions...GREAT! I'm not sure that it's the temperatur though. I probably ought to give you some more info.
Car has been parked for 3 years, so heaven knows what else is going to cause problems. Battery was completely dead - probably for more than 1 year, so I would suspect that any stored info is gone.
The idle issue that is arising appears to be exactly the symptom you described as an OPEN SYSTEM. Idles fast and fine when cold, but as it warms up, it begins a regular cyclic "bounce" between about 12-13 hundred and drops to about 600 or so for a sec then back up.
If I turn the screw on the ICV itself all the way in, the cycle becomes slower, if I open it all the way up, it cycles faster.
During normal driving, the engine appears to work fine (although a bit of a stutter at WOT on acceleration. Most likely, that problem is electrical (plugs, wires, etc.) I haven't bothered to track that down yet because other the the idle fluctuation, the engine runs STRONG. Was rebuilt about 40-50K ago, so I'm going to leave that alone for now I think - it's a minor stutter, not a serious drop in HP.
I'm thinking that the cycling is just too "regular" to be a vacuum leak, and I've blown about 1/2 a can of carb cleaner trying to find one. The initial problem (high idle) was probably due to the tons of carbon in the ICV. I did clean it. Now if I shake it, I get a rattle (like a ball bearing in a can of paint) when I shake it back and forth. Sounds to me like the piston is probably freed up and now working again.
I have changed out the DISGUSTING air cleaner. It had a very weird pattern of dirt on it too. Can't figure out how it happened, but there was a rectangle in the middle of the filter that was entirely black (almost looked like an oil stain). Anyway, breathes a lot better now too. I wonder if the dirty air cleaner was fooling the system......Hmmmm.
Would a dirty MAF sensor cause this? haven't cleaned that yet...
Sorry about the length, but I thought I'd explain as best I could.
Ok, so I'm getting ready to do the penny trick, and just for giggles, I popped my dipstick out to see if the loss of vacuum caused a difference. When I pulled it out, the rpms dropped to about 700 or so and steadied out. What the heck.
By pulling the dip stick, I think I'm introducing a vacuum leak, which should cause a hunting idle. It's working just the opposite.
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