Oil in #3 exhaust

[Raymond]

I had a tiny leak in the exhaust gasket.  So I finally pulled everything apart to replace it.  Now I see the #3 cylinder exhaust port has a thin, oily coating.  The other 5 are fine.  I had not noticed any performance issues.  The engine rebuild was 20,000 miles ago.  16,000 ago, I replaced the fuel injector on this cylinder.  Any guesses if it might be a valve seal or something more serious?

[Benz Dr.]

Do you see any blue oil smoke on start up or while driving? The more some you see the worse the problem will end up being. Valve seal or loose valve guide would be first in mind. look at how much remaining adjustment you have on the ball studs for that cylinder. If you've run out of adjustment, or close to it, you could have rocket geometry problems.

[ja17]

Ray, how has your oil consumption been?

[MikeSimon]

I am thinking maybe it isn't oil?? Unburned fuel over carbon deposits look like an "oily film" maybe the No 3 cylinder is running too rich and there is an issue with the FI pump?

[stickandrudderman]

I've had issues recently with heads leaking oil into the exhaust port.
I tried two different heads on the same car and the 1st head would leak oil into No 1 port whilst the 2nd would leak into 2 and 4.
No amount of crack testing, pressure testing, vacuum,  checking ball studs, fitting new guides and seals etc could eliminate the problem.
I ended up having to fit a new cylinder head and I still don't know what's wrong with the other two.
It's probably been the most frustrating job I've ever done in my 38 years as a tech.

[ja17]

It's strange that you mention that problem stick.  I had a cylinder head leaking oil from a head manifold bolt. The oil was being sucked into the intake port and then wetting one or two  plugs. The engine smoked only after high suction like deceleration. I removed all manifold bolts sealed the threads and installed a new intake gasket. The problem went away, but not before many hours of looking everywhere else.

[Raymond]

The oil consumption has been very low.  I'm going to change that injector for a new one simply because I have a new one on hand and it's so easy to access right now.  I'm traveling again so it will be next week before I can button her all back together.  Thanks for the thoughts! 

[Tyler S]

Dont forget to seal the ball stud bases where they screw into the head. These threads open up into the exhaust ports and if not sealed can leak oil directly into the exhaust. Giving the illusion of a bad valve guide.