Recently running m50nv misfiring and idling rough

[Oz10]

Hey guys,

Once again I need your help. So my m50nv is idling and running rough and I'm trying to trouble shoot the cause of it. I've sprayed the MAF with MAF cleaner, replaced the spark plugs, replaced a damaged spark plug boot, and cleaned the coil packs electrical connections. I just pulled the MAF sensor and it starting idling worse, so I don't think that's it.

The car starts up fine but then starts loping and the throttle response sucks. When driving it bogs when you give it any throttle. This issue has also been intermittent over the past few weeks. It has run perfectly at times then all of a sudden started running terribly.

I'm thinking it may be one or more bad coilpacks and I am trying to locate some to test this theory. I also think it would be helpful to test the coilpacks that are on the car to see if they are faulty or not. But I haven't been able to make sense of the How-To's I've found. Your advice is much appreciated. I'm trying to get my car running strong for a drift event this weekend. Thanks!

[greyis89]

Test each coil and the cps with an ohm meter compared to what specs should be. Do this with them unpluged from power. Is there any oil around the plugs? I was running way to rich for a while and found with my maf unpluged it runs better. Make sure your iscv is cleaned and good. I have a spare. Good luck and let me know what you find.

[Oz10]

i talked to Dave at Markert Motorworks and he things its a bad brake booster as I am having braking pedal issues too. Matt said I could grab the one of his black car so I'm going to go take it off tomorrow.

I'll definitely try that if the booster doesn't do the trick. Thanks!

[greyis89]

I am too. A slight leak at the booster to master cylinder but don't think it's enough to ruin the running condition that bad. I have a spare one of those too. We'll figure this out dude, it the little things. I'm glad you're up And running non the less.

[Wanganstyle]

i talked to Dave at Markert Motorworks and he things its a bad brake booster as I am having braking pedal issues too. Matt said I could grab the one of his black car so I'm going to go take it off tomorrow.

I'll definitely try that if the booster doesn't do the trick. Thanks!

stop by daves shop if you can, he can set you straight -

[Oz10]

stop by daves shop if you can, he can set you straight -

I picked up a booster from him today. Just put it on and haven't noticed a substantial improvement in the idle.

I did notice that one of the rubber grommets that attach the brake fluid reservoir to the master cylinder was worn and the other one missing! Could that cause the vacuum leak that is making my car suck at everything?

[Wanganstyle]

you do a smoke test to see if you have any big vacuum leaks? just find a fratboy and ask him to michael phelps your engine

or spray some brake cleaner in the engine bay while idling and see if it idles up?

did you change the garbage bmw design plastic crap outlets under the plastic intake manifold? there are a couple plastic nipple/coupling things that have o-rings that can go bad ; the nipples can also crack and give you a nasty leak.

also the intake manifold gaskets, those could be the culprit- my e39v8 and a former subaru swap had that issue.

Many older motors will need this service, M50nv is as Old as 24v gets. One former M50NV of mine had a stuck injector that ended up filling intake manifold and melting a hole in runner 6 of the m50 plastic intake manifold. Car would still run, but like SH*T.

[Oz10]

I cleaned the injectors today.

It'll idle fine for the first 5 seconds after I start the engine. The tach sits at about 800-900 rpms for that first five or so seconds. Then the tach starts to drop towards 600-700 for a couple seconds. Then the tach drops to right above 500 and the engine starts to lope and the car shakes. Anybody have any advice?

I think I might clean my ICV tomorrow.

[Oz10]

Aight i decided to go ahead and clean the ICV since it was still daylight. It was dirty, but I don't think that was the issue.

While the car was running I leaned down towards the pedals and noticed a faint hissing noise, like when you open up a coke bottle or something. When I pressed the brake pedal to the floor it would go away. That makes the think I still have a vacuum leak from the brake booster, even though I just put a new one on. Could I be missing a gasket or something?

[Oz10]

anybody?

[chadthestampede]

I recently had this same problem with my e34's m50nv and it turned out to be a bad coil pack. It would happen intermittently; sometimes it would be bogging down constantly, sometimes not at all. It was incredibly frustrating. It happened for a couple months before I finally figured it out. I had tested them all with an ohm meter and the resistances came out fine, but one of them was still bad. Only thing I can think of is that it had a really weak spark which would fire once in a while.

Sounds like the same problem.

[Oz10]

I recently had this same problem with my e34's m50nv and it turned out to be a bad coil pack. It would happen intermittently; sometimes it would be bogging down constantly, sometimes not at all. It was incredibly frustrating. It happened for a couple months before I finally figured it out. I had tested them all with an ohm meter and the resistances came out fine, but one of them was still bad. Only thing I can think of is that it had a really weak spark which would fire once in a while.

Sounds like the same problem.

My buddy has some spare coilpacks he said he'd let me use. Time to give that I try! Thanks

[Oz10]

I swapped out my coil packs for known good ones. And my idle seemed to improve. I just test drove it for a little bit. The car bogged a little at first, but started running smooth after it warmed up.

I'm still having weird brake issues. I'm having the same hissing noise and bad pedal feel that I had before. While driving it I noticed that anytime I let off the gas at all I would hear a high pitched whistling noise, almost like a tea kettle. That issue is new since I put in the replacement booster. If I have the car in neutral with the ebrake up and rev the engine the brake pedal goes up.I also noticed the idle go up and start running smoother when I let off the brakes. I'm guessing I still have a vacuum issue? I appreciate your help!

[328ijunkie]

Emailed you :(!

[Oz10]

ITS FINALLY RUNNING RIGHT!!!!!



The third brake booster was a charm!!