...or as soon as I open the hood to trouble shoot it.
My wife's 525 has had this problem for about as long as we've owned the car. When there is heavy rain the car misfires and the exhaust smells rich and sulfury. It never gives a CEL. Sometimes dropping it down into S3 and running it hard for a few minutes clears it up, but not always.
In past attempts to solve the problem I've replaced all the spark plugs (used NGKs, old ones didn't look bad) , and replaced all the coils (I confirmed that cyl #5 coil was faulty too). The plug insulating boots all look good, but are of unknown age. The grounding strap from coil #6 to the valve cover is there, and seems to be in good condition.
What am I missing?
I'll bet that GRM is faster and smarter than Bimmer forums, I placed this exact post over there this morning, and no one has replied
Its obviously water getting into something. I've noticed that the engine ground cable from the RH side of the engine to the frame is getting crusty, could that cause a problem like this? How about water intrusion into a damaged CPS or O2 sensor, I haven't noticed any damage on them, but they're both down low. All the major electronics seem well protected on these cars.
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