Hey, I just picked up a 91 626 for a grand, with 130k miles on it. Garage kept, owned by an old lady. Anyway, I never noticed smoke, but when I went to change plugs, cylinder 3 plug was covered in oil and buildup. I changed the plug and drove around the block, and the new plug already has oil on it. I tried to do a compression check and it read 130 on that cylinder, but I don't think I did the test right, i forgot to take out the other plugs, and I think my tester is junky anyway. Is there any easy way to tell whether it is valves or rings? Like I said, it's only the one cylinder, so I have a hard time believing its rings. Please help!

 

The reading on one cylinder is irrelevent (unless things are so bad it reads near zero), you need to test all cylinders and then look for any obvious differences. Let us know what you find out.

 

Valves (guides/seals) wouldn't likely be the cause if all you did was drive around the block.
I had what was diagnosed as a cracked ring in a Honda I once owned. It would've cost a lot of $$$ to repair and it didn't do any real harm, so I never had it taken care of.
I flogged that car for nearly 200,000 miles and it still ran great!!

So my advice to you is, if it ain't badly broke, don't fix it.

 

Compression check was good, all cylinders right around 160. I replaced the pcv valve, found a small amount of oil residue in the pcv hose and nipple, so maybe it was finding its way into cylinder 3? If its not that, then it's probably a dripping valve. Anyway, it doesnt smoke, so it cant be much, its just blackening that one plug.

On a lighter note, I found a thread saver on one of my plugs, which the previous owner was unaware of. Thanks, dealership!

 

Still think you've got a cracked ring, or an oil control rting that's slowly failing. The symptoms are the same as what I had.
But as I said before, I wouldn't worry about it when or until it becomes a real problem.