2001 yukon denali 6.0 oil in cylinder 1 and 3

I have a 2001 gmc yukon denali 6.0. I had taken my car to a mechanic to get a dionostic and he told me I have oil in cylinder 1 and 3. He said he cleaned out the oil and it came back when he started it. It runs with loss of power and has a random misfire code. Is there anything I can try before replacing my head gasket

Welcome to the forum from Oregon.

Sorry about the problem with your truck.

Miles on the engine? Random misfire code for 1 or 2 cylinders are are/is for cylinder 1 or 3 or both? Oil in cylinder can foul the plugs. Were the same plugs reused when "cleaned out" and restarted? How was the oil cleaned out? Was a dry and wet compression test ran? If so, what were the results?

OR VietVet said:

Welcome to the forum from Oregon.

Sorry about the problem with your truck.

Miles on the engine? Random misfire code for 1 or 2 cylinders are are/is for cylinder 1 or 3 or both? Oil in cylinder can foul the plugs. Were the same plugs reused when "cleaned out" and restarted? How was the oil cleaned out? Was a dry and wet compression test ran? If so, what were the results?

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The engine has 193k miles and I don't know how the oil was cleaned out and yes the same plugs where used. The code says random misfire and he told me it's for cylinder 1 and 3

Either the rings are letting oil in from the bottom,
or valve seals are letting in oil from the top.
How else would oil get inside a combustion chamber?

Old plugs were likely fouled. Can cause a misfire, even if oil is not getting back in. Compression test, dry and wet, is needed.

Marky Dissod said:

Either the rings are letting oil in from the bottom,
or valve seals are letting in oil from the top.
How else would oil get inside a combustion chamber?

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Could be that the pcv system has flooded the intake manifold with oil and that is getting in the cylinders.

tendempine said:

I have a 2001 gmc yukon denali 6.0. I had taken my car to a mechanic to get a dionostic and he told me I have oil in cylinder 1 and 3. He said he cleaned out the oil and it came back when he started it. It runs with loss of power and has a random misfire code. Is there anything I can try before replacing my head gasket

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Head gasket replace for oil in the cylinders? Watchu talkin' about Willis????

Youve got oil running down valve stems because of bad valve seals or you have bad rings on those cylinders. A compression check across all 8 cylinders will tell you whats up with your rings. Otherwise pull your valve covers and plan on replacing the valve seals when you take them off.

tendempine said:

I have a 2001 gmc yukon denali 6.0. I had taken my car to a mechanic to get a diagnostic and he told me I have oil in cylinder 1 and 3 ...

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Mudsport96 said:

Could be that the pcv system has flooded the intake manifold with oil and that is getting in the cylinders.

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Cylinders 1 & 3 only?
And this likely has nothing to do with a head gasket.

Marky Dissod said:

Cylinders 1 & 3 only?

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I haven't cut open a manifold to see what cylinders are closest to the pvc hose port. So it was a guess and less of an absolute. But with the known oil consumption issue because of valve cover issues, it is as good of a place to look as any.

If you have oil in cylinder 1 and 3 you should look with endoscope into the cylinder, to see where the oil comes from. If it's the valve stem seals, what is very likely, then you see that, when the valve is opened.

Miss firing has nothing to do with that, except you have a lot of oil in the cylinder.

Missfiring can, as others here already mentioned, has to do with old spark plugs, problems with wires, or lose connectors of the injection valves, what I had recently.

So as from @OR VietVet already recommended, I would also first do a compression test, to have a picture of the mechanical situation of the engine. Then look with an Endoskop through the spark plug hole into the cylinder and check if the oil comes from the valve stem seals. Change as well spark plugs and check the ignition wires.

Valve stem seals can be exchanged without removing the heads...

The PCV is also a possibility, but I don't believe that you would have the oil then only in cylinder 1 and 3.