nagging misfire problems - help please

[Reed]

I've been getting misfires with only a "misfire" code thrown on the BMW scanner. It has only happened on the track and seem random. Happens at full tank, half tank, has happened in first session when car was cold and midday when it was hot. Other time it is fine. Seems to happen more when the car is pushed hard though. In hope of curing this I've replace the fuel filter, front oxygen sensors, and yesterday the coils. The session after the coils were replaced it had no trouble but the session after that misfires again. Btw, it has misfires in 2, 3, 4, 5, and 6 but not 1.

The car does NOT have a chip.

Where to go next - knock sensor? I only run 91 from Chevron or 76. I just ran Techron concentrate through as well but it whould have been clean before that.

Fuel pump? Maybe it is not supplying enough or the pressure regulator? One specific instance was the bank at California Speedway branking hard coming into a 90 degree turn. Had been WOT around the bank and then brake, shift to 3rd and then the misfires started. Other times it has been just going to WOT after a long, steadily increasing throttle application. But on the other had it happens under different circumstances.

I'm at a loss - any help will be greatly appreciated.

[Nimble]

I had misfire issues for a while, and like you I replaced.

-spark plugs, the back 3 banks had oil on them, so I also replaced the valve cover gasket, which you should do if you haven't already

-coil packs, my number 2 bank had a misfire code, seems fine now

But, my fuel pump failed on me, so that has been replaced on my car in the last year as well. Maybe you should try that and a plug, VCG replacement.

Not sure how knock sensors tie into the misfire though.

[Reed]

I had misfire issues for a while, and like you I replaced.

-spark plugs, the back 3 banks had oil on them, so I also replaced the valve cover gasket, which you should do if you haven't already

-coil packs, my number 2 bank had a misfire code, seems fine now

But, my fuel pump failed on me, so that has been replaced on my car in the last year as well. Maybe you should try that and a plug, VCG replacement.

Not sure how knock sensors tie into the misfire though.

New plugs were put in recently and there is no oil contamination in any of the plug wells - forgot to mention that but I think I'll pull them to check the tips just in case they are fouled or something. I'll look at the VCG while I'm there too.

I was told I might want to try the knock sensor since the coils and other things didn't fix it. Maybe grasping at straws but from what I was told, the knock sensor might retarding the timing if it is faulty. Not sure how tha tworks but it was one suggestion I hadn't heard before.

[JLac]

If all else fails try a compression then a leakdown test.