A buddy of mine has a 91 740 that is currently running rough at idle and has a CEL on. He took it to a mechanic who told him that his spark plugs were coated in oil. The mechanic wants waay too much money to perform a stage one tune up, so I agreed to help my buddy do it himself (in exchange for a 6 pack ) I am going to first pull the codes and then go from there. I also plan on helping him clean the throttle body and idle motor, since I hear it often needs to be done on these engines. My question is, what can be causing the plugs to supposedly be covered in oil? The car is non-turbo and has something like 165k on it. My friend claims it's not smoking blue, and that once it gets up above 2000 RPM it runs a bit better. I drive a 960 and am familiar with it. The 740 will be a new game, so any suggestions would be appreciated.

 

Haynes Manual says:
Oil fouling:
worn bores/piston rings or valve guides.

 

My Vote is valve cover leaking some and when the plugs were pulled out the oil ran down the plugs.

Or maybe the fuel pressure regualtor is bad and it is flooding out.

 

I was also thinking worn rings........but it only has ~165k on it. So unless it has been seriously neglected I would hope that it's the valve cover. I guess we'll just have to tear into it and see what happens.