88' 325ix. Starts fine, idles fine. Starts to run rough and stumble at 2500 through 3500. At 3500 stops misfiring and runs great. Does it under load and in the drive way.

I have:
Adjusted the valves
Cleaned fuel injectors + new seals
replaced all hoses and double checked em all
New valve cover gasket
New Fuel Pressure regulator
New used o2 senor
plugs
Crank position sensor
exhaust seals and new exhaust

Running better of course but none of that made any difference in the stumbling.

Any thoughts are very much appreciated


Amazing of guys to offer this kind of help!


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This post was auto-generated based upon a question asked on our tech article page here: Pelican Technical Article: BMW E30 3 Series Idle Speed Troubleshooting

You've already replaced just about everything! I would revert back to old school here, and actually check the timing of the engine with a timing lamp. Sounds like it may have something to do with the mechanicals of the engine, rather than the injection or the ignition (since it runs fine everywhere else). Also run a compression check while you're at it, just to verify the condition of the underlying engine. But, I would suspect something is up with the timing at that rpm range.

- Wayne