Rich running, high idle, and misfiring walk into a bar...

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nedfunnell

Senior member
Nov 14, 2009
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I have an ongoing but intermittent issue with my 85 325e. For a while, it has been running rich. I has had an on-and-off misfire/stumbling issue. Lately, this got more interesting (and severe) and I would like your input. Here are the three symptoms:

1. Running rich. Sometimes more rich, sometimes less so.

2. Idles high. It varies between 1500 RPM and 2700 RPM when this issue is present. It never idles high when cold, but is now consistently idling high when hot. It is getting extra fuel and air somehow to cause this: enough to cause the high idle, and enough to give me unwanted power when going slowly: I can put it in 3rd at 20mph and accelerate to 25 and and beyond with my foot off the gas completely. It's weird to shift at 2500RPM and have your revs go up when you clutch out with your foot off of the gas. This part is consistent- car gets warm, idle gets ridiculously high.

3. Really bad misfire/stumbling issue happens when driving sometimes. The bad, not-all-my-power-strokes-are-happening-and-I-have-no-power kind that makes your car lurch back and forth. This usually goes on for a minute or two and then smooths out. Seems to be better at higher RPM if I can get there. This part is really intermittent. Happens rarely (that is, once a weekish) but freaks me out badly every time.

I thought of a vacuum leak, and replaced the hose to my idle control valve- didn't affect it. My intake boot is only a few months old. There could be another one somewhere. I did the test of taking the vacuum hose off of my fuel pressure regulator and waiting for an RPM rise. The rise did happen, albeit slowly and after a slight delay. The plugs and plug wires are recently new. The PO changed out an O2 sensor before I got the car (10k miles ago?). Could it have gone bad again due to an underlying issue and have this problem?

What should I look at next?

Note: Moved from a BMW forum I don't think I'm going to frequent anymore. Can anyone recommend a good one?
 

nedfunnell

Senior member
Nov 14, 2009
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Also, since the title of this thread promises funny and doesn't deliver, here's a mildly humorous anecdote from the garage:

I am fixing the radio in my BMW. I thought it was broken, but it turns out it was a wiring issue. Let me preface this by saying that I figured something unusual was going on when I connected the replacement radio and heard the power antenna going up. Getting in deeper, I realized that I was getting battery voltage across the power wires, but no power- it wouldn't light up a 12v bulb even though I could measure 12v across it. "Aha!" I said to myself. "A bad ground!" Not unusual. What IS unusual, though, is that when I traced the unusual-looking wire that was my suspected ground, it was actually one of the power cables for the ANTENNA MOTOR. HMMM. Ameteur car radio wiring: It's Bad, Every Time!™ Also, all the wires for the rear speakers that went into the electrical tape bundle full of butt splices... ended there. No clue where my rear speaker wires are.

Note: I did get the car from manimal, but this wasn't his wiring job. This was the one before his. Don't hate him.
 

manimal

Lifer
Mar 30, 2007
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Sorry your having trouble Ned. Come by the shop this Saturday and we can have a coffee. I'll ask the old girl why she's running rich. Old gals sometime need a little attention.
 
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