1992 525i project runs rough

[Guapo]

Check your coil boots for arcing inside the spark plug tunnel inside the head. I had similar symptoms when I had a bad boot.

[wiebuschk]

What would an arcing boot look like?

Drove it today. Runs better but not right. I still think its lean but there is no vacume leak that I can find. ??

What could cause this that would not throw a code?

[wiebuschk]

The problem ended up being a bad #2 coil. Found it by pulling coils one at a time. When I pulled the #2 the way the engine was running did not change. I still have a slight stumble off idle if I nail it but it is much better than it was.
Thanks for all the advice!

[Dave M]

Thanks for following up. I've been following the post and appreciate it when the culprit is reported.

[foemill]

I've been following this thread and my '95 525iT has been having identical problems. I checked the coils and they all read 7.9 - 8.0 ohms though. did you check your coils as well? The rough low-end performance has been driving me ! And like yours, it runs great before the car warms up. I'll try pulling the coils one at a time for a sanity check. Were any of your plugs wet at all?

The problem ended up being a bad #2 coil. Found it by pulling coils one at a time. When I pulled the #2 the way the engine was running did not change. I still have a slight stumble off idle if I nail it but it is much better than it was.
Thanks for all the advice!

[genphreak]

Thanks for following up. I've been following the post and appreciate it when the culprit is reported.

Did anyone resolve the great M50 mystery? I've found similar threads around- at least 10 other occurences of intermittent stumbling as if 2 cylinders died whilst running- but then they cut back for apparently no reason. I also get the occasional intake backfire on cranking.

No solutions have been found, excepting the intake gaskets Jon was suggesting.

Is this a vacuum leak after all? I'm almost sure it can't be on mine- I've done everything. Next step for me is the O2 and temp sensors... then it gaskets .

Any suggestions would be greatly appreciated of course.

[genphreak]

I generally fixed the engine backfire, dodgey running and slow (500rpm) idle by replacing vacuum pipes... what so clearly seemed to be a coil or a plug or a cylinder was actually the vacuum pipe between the cam cover and the intake junction (plastic pipe leading into the intake manifiold behind the throttle body). I've checked the Idle Control Valve, the throttle body, all the other connections (ie 'PCV' and throttle hoses off), I don't know why I didn't check the front one... it also has a white o-ring, so no doubt that has to come out.

So don't go off symptoms with your troubleshooting, what the computer thinks when you have a vacuum leak will make it do unexpected and weird things indeed.... Nick