2007 Denali Cylinder 6 Oil Foul

[Keoder]

Apologies if discussed ad nauseam, but I need some help. My 07 has 134,000 miles and I have had cylinder misfires in #6. Pulling the plugs, it’s clear #6 is fouling because of oil. My question is, from what you all know about these 6.2s, is this a bad ring or a valve seat? It takes some time for the plug to go bad and misfire m, but it will eventually.

Thanks in advance for your help.

 

[OR VietVet]

By, "takes some time", what are we talking about? Need a compression test and a cylinder leak down test. Or just keep throwing plugs in there till you have the extra cash for a teardown and repair.

 

[89Suburban]

Add an oil catch can.

 

[Keoder]

By, "takes some time", what are we talking about? Need a compression test and a cylinder leak down test. Or just keep throwing plugs in there till you have the extra cash for a teardown and repair.

I’ve replaced all of them once before...maybe at 115,000 miles. It doesn’t foul up in one or two drives.

Is that common with these engines? Best case am I looking at new valve seals?

 

[donjetman]

One yr ago, my 07 Denali 6.2 w/132k miles was burning and leaking 1 oz every 100 miles.
I installed a catch can, did GM TSB# 10-60-01-008M, installed the new improved valve cover, replaced the rear main seal, oil pan gasket, then It immediately stop using any oil. Now 1 yr & 18k miles down the road it still doesn't use any oil. Here are some threads I did that will help you.
https://www.tahoeyukonforum.com/thr...tor-oil-consumption-tsb-10-60-10-008m.108493/

https://www.tahoeyukonforum.com/threads/rear-main-seal-job-pan-etc-07-yukon-denali-6-2.108334/

https://www.tahoeyukonforum.com/threads/valve-cover-change-cleanup.108604/

https://www.tahoeyukonforum.com/threads/sparkies-no-beno.108579/

 

[Keoder]

One yr ago, my 07 Denali 6.2 w/132k miles was burning and leaking 1 oz every 100 miles.
I installed a catch can, did GM TSB# 10-60-01-008M, installed the new improved valve cover, replaced the rear main seal, oil pan gasket, then It immediately stop using any oil. Now 1 yr & 18k miles down the road it still doesn't use any oil. Here are some threads I did that will help you.
https://www.tahoeyukonforum.com/thr...tor-oil-consumption-tsb-10-60-10-008m.108493/

https://www.tahoeyukonforum.com/threads/rear-main-seal-job-pan-etc-07-yukon-denali-6-2.108334/

https://www.tahoeyukonforum.com/threads/valve-cover-change-cleanup.108604/

https://www.tahoeyukonforum.com/threads/sparkies-no-beno.108579/

So I’ve replaced the oil pan gasket and the rear main already. Not the valve cover gasket.

Will adding an oil catch can make a big difference?

And in your thread where you posted pics of the plugs, mine was like your fouled one but black.

 

[89Suburban]

I’ve replaced all of them once before...maybe at 115,000 miles. It doesn’t foul up in one or two drives.

Is that common with these engines? Best case am I looking at new valve seals?

Clogged PCV valve?

 

[Keoder]

It’s a permanent valve from what I gather.

 

[donjetman]

The valve cover needs to be changed, not the gasket. Read the links I provided. The PVC IS the new improved valve cover, # 12570427 (for my vehicle). There is not a traditional type PVC that can be replaced. What is happening with the original valve cover design is its allowing oil to be sucked from the valve cover, into the intake manifold, into the combustion chambers, where it is partially burnt, but it also causes the pistons rings to become stuck, and then even more oil is consumed because it is able to get by the piston rings. Alas, GM TBM 10-60-01-008M.

The catch can really isn't necessary if all goes well like it did with mine. But I left mine in place and if it ever starts collecting any oil in quantity again, then Houston we have a problem.

 

[Keoder]

Ah, I see.

If I run a compression test, would I get good reads in each cylinder and thus know for sure it’s a PCV issue?

I’m not savvy enough to put on a new valve cover but I do want to be able to tell the mechanic...”Here’s the issue. Please fix it.”