***Very Rough idle and stalling!! HELP***

[BMW325issport]

***Very Rough idle and stalling!! HELP***

okay so today i took the whole manifold off my 1998 m3 and replaced the oil separator vacuum lines cleaned the idle control valve with starting fluid, cleaned maf with contact spray replaced intake boot and practically every hose. I went to start it up and it starts and it revs around 2000 rpms for like 4 seconds then in tries to idle but idles very very rough and then stalls. What could be the problem?? What would cause it to rev high on startup then stall out? Vacuum leak? Any ideas would be great thank you.

[M3GeeTeeR]

Try checking all the hoses one by one if you haven't already done so, to make sure they are properly seated and/or clamped securely. Sometimes a slight mis-aligned hose can cause a big problem. Also, check the MAF sensor as they are very sensitive to any grime deposit that may get caught in there, and could be the cause for any irregular engine operation.

[BMW325issport]

it was a crack in one of the hoses. Thanks

[M3GeeTeeR]

Yep, a crack in one of the hoses will cause those problem. Good job finding the culprit.

[BMW325issport]

Well it wasn't that hose. Replaced it and it still dosent wanna idle and running really rough. Also starting to backfire and miss. I'm stumped there's no way a little vacuum leak can cause all this.

[FlyLizards45]

My rough idle culprit was found to be an aftermarket TB. Idle was fixed after OEM TB was put back in

[Manantodd]

Unplug your MAF then start the car. If it idles fine, then your MAF is bad. Happened to me last week.

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[thomasetti]

Stuck closed iac? Or stuck open ccv valve?

[sjpgoalie]

Unplug your MAF then start the car. If it idles fine, then your MAF is bad. Happened to me last week.

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Not so usually with OBDII e36s. That trick usually works on OBDI cars, but OBDII cars usually won't start or die with the maf unplugged. For some reason a lot seem to run better when it is plugged in with a bad sensor as opposed to disconnected. OP most likely has a vacuum leak on the fat, fat like that runs under the manifold.


OP, was it down on power before this happened? Has it been maintaining coolant levels?

A clogged oil line could back up too much oil I suppose. Pull the plugs and look in the chambers. Note a lot of oil or one or two pistons that are cleaner than the others.

Dumpy idle with backfiring could be anything from poor compression to a crank or cam sensor.

[bweier]

A bad cam shaft position sensor will do this...getting my replaced today as a matter of fact...but it seems like you would get a Check Engine warning if this was the case. A clogged or dirty CCV could be a culprit as well. When's the last time the spark plugs were changed? Coil overs? I agree with pulling the plugs for a visual...might be a good time to change them if you are due. If so, consider the 4 prong coppers (or whatever OEM copper was speced) over the platinum or iridium...you will be glad you did!

[BMW325issport]

Thanks for all the info guys. It turned out to be a bad CCV grommet. It was cracked down the middle and wasn't seating the separator correctly causing a vacuum leak. Problem solved