Misfire Cylinder 1

[stuntflyer]

Originally Posted by c-bass

I was lurking a bit to see how things would play out but I'll throw in my 2 cents.

My issue was sort of the reverse of what you are experiencing but the symptoms are quite similar.

During idle it would trigger misfires and run very rough. If I turned off the engine and restarted it would run fine until you hit the first red light. If I kept the RPM up over 2k and then quickly put it in drive it wouldn't exhibit the misfire.

Replaced the CCV, swapped out the idle air, coils and all the usual suspects without being able to get rid of the stumble at idle.

Finally I built myself a poor man's smoke tester and noticed smoke coming from "the middle" of somewhere. Seeing as pretty much everything else that was a gasket had been replaced my logic said to replace the gasket on the intake manifold and that did the trick.

I found a gasket on amazon for about $10 and it's been behaving ever since.

In my case I didn't even disconnect the fuel rail. Just lifted the intake off enough to replace the gasket.

You can read all about my experience here https://xoutpost.com/bmw-sav-forums/...hate-bmws.html

Also, the ambient air/fan issue you're thinking of is non existent when you're doing a smoke test because the engine is off...right?

Hi - yup if you pressurize the plenum with smoke that could definitely localize a vacuum leak, or in your case, a gasket leak. In my case, my problem only happens when I rev the engine, under load, above 5000 RPM now, so not sure a standard smoke test will help me, but, I will give it a try next week before I go pulling the intake plenum off again. My engine idles perfectly, and runs super smooth, as long as I never rev above 5000 RPM (its not like I am up in those revs very often, but there is an issue, so I need to figure it out). It is only when I accelerate to come up to highway speed (for example) that the issue shows up. Otherwise the thing runs really nice. I replaced my CCV and all the vac lines a year ago, so I know those are all in good order.

I'm surprised you were able to get to all the nuts that secure the plenum to the intake without removing the rail - the rail/harness assembly kinda blocks access to some of those nuts. I guess with the right universal attachment you can get to them. On that note, I will go double check that mine are all secured as well.

Thanks for the comments. My quest continues. Will see if I can find anything with my homebrew smoker this coming week.