Fouled Spark Plug

[professor]

#1 had a hard caked deposit.
I checked compression on that cylinder and it read: 180 psi and stayed there until I bled it.
I put a new spark plug at it came back fouled a day later. It had what looked to be oil.

1. I don't think it's the piston ring since the pressure held
2. I suspect a valve guide or valve stem seal
3. This must have contributed to my illusive stalling for sure.

Ah, let's not forget, this is a 1988 190E 2.3 8V.

I am now at a crossroad:
1. Should I do a complete head job?
2. Just replace the steam seal and pray that would do it.
What are your thoughts?

[professor]

Oh, I also measured the vacuum at the intake and I was getting a fluctuation between 16 and 20 Hg at idle then it was nice and steady at higher rpm.
Could this be an indication of a worn valve guide?

[pawoSD]

Usually its the valve stem seals, and possibly the guides as well if its a real high miles motor.....it allows oil to be drawn in and burned....fouling the plugs. My 300E has been doing this to the #5 and #6 plugs.....I just clean them occassionally.....if yours fouls real fast then its time to do the seals and possibly the guides if its a 175k+ engine.

[professor]

mine is so bad that I think it is the main culprit in my stalling saga

[Ivanerrol]

Originally Posted by professor

mine is so bad that I think it is the main culprit in my stalling saga

You're probably right there. You can get a leak down test done to show up leaky valve guides and seals. Or just get your head rebuilt.

[professor]

I tested the vacuum at idle and the needle was dancing between 16 and 20 (mytivac) but it was steady at higher rpms.
I tested the compression on cylinder #1 and I got 180 psi and it stayed there nice and steady until I bled my tool. This eliminated the possibility that I have a stuck or unseated valve or piston ring wear.

[Chas H]

Oil getting past a ring or a valve guide/seal will have no effect on a compression or leakdown test.

[professor]

That's clearly the case, my worry was a worn cylinder ring which would make my eventual repair a pita.

[Chas H]

Originally Posted by professor

That's clearly the case, my worry was a worn cylinder ring which would make my eventual repair a pita.

These engines have a history of valve guide/stem seal oil leakage. I'm not sure if the stem seals can be changed with the head in situ. If they can, that would be the repair to make. Then see what happens.

[Hirnbeiss]

Is that the only fouled plug? How are the vacuum hoses and the crankcase ventilation?

[professor]

Originally Posted by Hirnbeiss

Is that the only fouled plug? How are the vacuum hoses and the crankcase ventilation?

Yes, it's the only fouled one. All vacuum hoses are brand new.

[professor]

Do I have to remove the cam tower to reach the stem seal?

[professor]

Okay, I took the cam tower off after seeing this thread: valve spring compressor

But how does one go from this


To this

???

I compressed the spring with the same exact tool but I couldn't figure out how will the spring come out? Then how will it go back in and lock in place?

[Hirnbeiss]

You compress so that you can remove the retainer on top (fits into the groove on the valve stem). Note also his compressed air into the spark plug hole so the valve doesn't drop down.

[professor]

I couldn't access or see the retainer... Is it a C or E clip? All I noticed is a loose spinning top where the hydraulic tapper meets with the valve spring.