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View Full Version : very rough iddle M50



Jose
12-19-2004, 06:53 AM
Just bought a '92 325 i coupe (without the vanos) for my girl, and it has been running great for a couple of days up until today and now a very rough idle has develloped and the engine even wants to stall when your cruising, only full throttle keeps it going in combination with a lower gear reving it past 5000 rpm.I've checked all vacuum hoses and they were fine.
What puzzles me , is that when putting your ear on the inlet manifold and throttling the engine , yoyu seam t hear the same "suction "noise you hear at the afm.
Something tells me that it must be false air leaking somewhere past the throttle body as today it even backfired wit a loud bang.I had the same experience once with my other car whichruns on 48 mm Weber carburators and that turned out to be false air. It's the first time I experience this "behaviour "on a BMW as I usually take the engine apart for a overhaul after buing a car with more than 150.000 miles on it. Anyone got a clue out there ?

DueyT
12-19-2004, 05:35 PM
Jose, did you do just a visual on all the plumbing bits between the AFM and the manifold? There may be some sneaky leaks hiding there. Not an M50 type of guy but something happening that quick seems like a cracked vacuum fitting downstream from the AFM. If you have a can of carb cleaner, you could try shooting little squirts around fittings between the AFM and the head...I rise in engine speed will often point to the leak.

Cheers,
Duey