Hi,
I have a 92 400E with 90K miles, which has picked up a rough idle, like small, quick surges. I pulled a plug and noticed it was somewhat wet. I seem to remember having read somewhere that transmission fluid can get into the engine somehow, and I have been having to add transmission fluid, (automatic), lately. Could that be the problem, and if so, how would I check to know for sure.

I have not yet changed the ignition harness, which from all I have read, will be required soon. If that might be the problem, how would I check that?

Thank you for all the good postings and for any advise you can offer here.