S52 Misfire at 3500-4000 and above

[CameronG]

I seem to have developed a misfire on my S52 and am struggling to locate the problem. All spark plugs are good, all coils are good, vanos is okay, maf is okay. I honestly am not sure where to look. The only thing I can come up with would be my CCV. It has been deleted and is currently venting excess gas and oil directly to atmosphere. From my experience with these cars, this theoretically shouldn't cause the problems I've been having, but maybe someone who knows more than me can help me out. The problem I am having is completely random as to when it will actually misfire, in relation to how long the car has been running, but once it starts, it will not stop until I shut the car off and let it sit for roughly thirty seconds. On initial start up and when I start it after having turned it off to try to correct the problem, it will start and idle perfectly. Only when I go above 3500RPM will it start again. The car was initially running fine, but after about 7-8 months of driving it without the CCV is when it started to develop these problems. Does this seem like it could be related? Is there a way to route a catch can so that I can run the vapors from the catch can back to the intake, therefore having no vacuum leaks? I've searched but did not find anything very similar to my problems. Hopefully this is something someone else has experienced and been able to correct.

[ScotcH]

cam or crank sensor?

[Hova]

cam or crank sensor?

This. I had a bad cam sensor and had constant misfires.

It should throw a check engine light as well.

[BimmerBreaker]

The only thing I can come up with would be my CCV. It has been deleted and is currently venting excess gas and oil directly to atmosphere.

Thats not right

[tjm3]

.... Is there a way to route a catch can so that I can run the vapors from the catch can back to the intake, therefore having no vacuum leaks?....

Put the original parts back in. You're not likely to re-engineer a better solution.

[CameronG]

Thanks for the replies. I checked resistance of the cam sensor and it seemed to be okay, but I may just go ahead and replace it along with redoing the original CCV set up and hope for the best.

[Hova]

Thanks for the replies. I checked resistance of the cam sensor and it seemed to be okay, but I may just go ahead and replace it along with redoing the original CCV set up and hope for the best.

Try doing the same test when the unit is hot. I had a very strange issue where I had no misfires when my engine was cold, but once driven for 15+ minutes, it would misfire like crazy. The resistance when hot vs when cold was way different. Just something to keep in mind.

[BMWManiac]

With misfire, I would work backwards...do you have a scan tool? Are you misfiring in all cylinders? Check the easy stuff....plugs, boots, coils, coil harness, ground wires on the valve cover.

[cmoody]

We had something like this develop due to dirty injectors, but it showed at high rpms at high load only; turning the car off and on again fixed it until the next time we made it happen. I'd dump in a bottle of Techron and see if that has any effect on where the misfire occurs in the rev range and under what load conditions. Ex: if the misfire occurs at 5500 when the car is in neutral and you're just revving the engine vs. 3500 when you're in 4th going up a hill.

[ScotcH]

Also, look for water in #6 plug well ... or oil in any of them

[ChrisB41]

Hope you got it fixed by now, but any codes? I have catch can and it does not misfire.