[SOLVED] Cylinder 1 Misfire - P0301 / P0300 Mystery

[Toothbrush]

Originally Posted by pshovest

Smoke test suggests there is an exhaust valve leak. Certainly worth it to pull the valve cover and inspect, though I can't envision an improperly installed valve seal preventing a valve from closing completely. You can check that valve keepers are installed properly and that valve train gear looks identical to the other exhaust valves. Might put a straight edge across both cyl 1 exhaust valve spring retainers, they should be the same height. If they're not, then one is open/damaged.

Thanks! That'll be my next course of action. Cylinder 1 was the first set of valves I changes the seals on, so it's certainly possible my lack of experience and quality of work is the issue.

Originally Posted by pshovest

You can remove the valvetronic gear, forcing valves to close and check compression again. If it's still low you get to pull the head.

This part I'm not quite clear on. Are you saying unclip the electric connection for the actuator (part # 11377548389) or unbolt it? I have uncliped it in the past to see if it affected the misfire, but have not done a compression test with it disconnected.

Originally Posted by pshovest

Did you have any trouble re-timing the engine after valve stem seal replacement? Any piston-valve contact while turning engine over?

I did the seals in the vehicle without removing the cams, so did not touch the timing.

As for piston-valve contact, I don't recall ever hearing anything other than air when hand cranking, any time I've ever done that and I can't see any obvious damage to the piston or valve. Though from what I have read I suppose the only way to be sure is a close visual inspection with the piston clean and/or measuring clearances. ?

Edit: Here are the results of the OTC injection cleaner (1 can) and CarbonClean MV6 (2 cans). Results for the top of the pistons are positive, though not as impressive as I would have guessed. The valve stems look roughly the same, however, getting a good image is very difficult at this time. I've attached comparison pics for Cylinders 1 and 2 and pointed out some differences.

Note: For Cylinder 1, I had previously soaked it overnight 3 times using Acdelco X66P Fuel Injector Upper Engine Cleaner, which is why it looks so much cleaner and you can actually see parts of that piston without contamination, thinking the Piston Rings might have been the problem (obviously not now). That product did much more to clean the top of the piston, but obviously can't do much for the valves as you just pour and soak, then remove. Although, I have had fleeting thoughts of getting the exhaust valves open and then filling the cylinder up as much as possible without getting the cleaner in the exhaust port to see if I could get at least some of the valve/s soaking.

There are some videos for other BMW owners using it for Ring related misfires with good results. Cylinder 1 looked just like the other 7 until I soaked it with X66P, in case anybody mistakes it's condition with a head gasket problem.