fouling plug #3

[marc79euro645]

I keep fouling plug 3 on my 84 m106. I swapped injector 3 for #1, to see if the fouling would follow the injector, it didn't. It appears to be oil. I checked the lower charge tube to see if turbo seal had blown, no excess oil there. I checked dipstick, a little low, but no sign of water.I checked compression. These numbers are all low, I don't trust the gauge as the motor has been solid for 2 years now,but here they are
1-90psi
2-90psi
3-100psi
4-100psi
5-80psi
6-80psi
so #3 is one of my best. I guess Ill check valve stem seals next. any thoughts appreciated.
marc

[marc79euro645]

Well, I pulled the valve cover, but I can't see anything. two piece springs w/damper completely hide the seals. Has anyone ever actually changed stem seals with head on car?
I also checked my compression gauge, and it matchs my compressor,so I guess this motors just worn out. What is acceptable compression?
thanks
marc

[jim325]

I dont think you will be able to change the valve seals in the car inless you pull the rocker arm shafts out. I tried pulling valves out of my cylinderhead to lap all the valves and there just wasent enough room to get the valve spring compressor in after sliding the corresponding rocker over. Maybe you could do a couple but not all of them.

Can you burrow or rent a leak down tester? That would help to see if its worn rings, valves, or valve seals.

I thought i remember 185 psi being good compression but i could be wrong.

[Bill in MN]

This past spring this same thing happened to my #4 hole in a new motor with perhaps 8 hrs on it. I'd change out the plug, it was soaked within seconds. It had compression (albiet, low) and leakdown numbers were borderline OK. Upon teardown I found oil in places it had no business being....such as on TOP of the #4 intake valve. Just on the valve, though, not in the intake manifold or anywhere else.

The offending hole was a goner but it was no obvious until the piston came out. The top of the piston was visibly in good shape and a cursory glance with the head off told me the motor was OK. It wasn't.

One theory was that the hole detonated and there was compression enough to suck oil past the rings and into the chamber. The other theory was that somehow oil was getting into the chamber, igniting and ultimately causing it to detonate. I still have no idea as to what really happened, other than my checkbook taking big ol' shit kicking.

[marc79euro645]

hallelujah!
It was the coil high tension wire shorting out to the chassis. I was really getting depressed. I just don't want to have to pull the motor again. I still don't understand why #3 was the one that kept fouling, or how it ran at all as the wire was really toasted, right where I couldn't see it. She's running great now though.
thanks
marc