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Discussion Starter #1 (Edited)
I have a 2006 CTS 3.6 105k miles. I got a misfire so I decided to change the plugs. Noticed that all of the plugs have excessive oil On them and in the tubes. I replaced the tube seals in the valve cover, valve cover gasket, plugs, coil pack on the misfiring cylinder. It ran great for about 10k now the misfiring has came back and now on multiple cylinders and all the plugs are covered in oil again. The only 2 codes besides misfires is O2 sensor, and catalytic converters. No smoke, no overheating, coolant ok. Any advice?
 

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Go ahead, blame me. Everybody does 馃檮
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Please move this thread to the 1st Gen CTS subforums.
 

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2008 SRX4 & 2010 CTS4 sedan / Non-Cadillacs: 2018 Audi Q5, 2012 Chev Cruze LT
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You'll find lots of help there. Given the age of the car, I suspect that the valve cover and spark plug tube gaskets need to be replaced. It can be a DIY job depending on your skill level, of course.
 

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08 CTS DI
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The first time around would be the seals in the valve cover, the second time in 10k miles points to defective/porous cylinder heads that GM issued a TSB on, stating they are to be fixed with new heads. You can remove the valve covers and clean thoroughly around the spark plug tubes with a solvent at the tube insertion point in the head and then force an oil resistant sealant (RTV Grey I believe) into the crevice around the perimeter that should cure the problem if done well.
 

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Discussion Starter #7
The first time around would be the seals in the valve cover, the second time in 10k miles points to defective/porous cylinder heads that GM issued a TSB on, stating they are to be fixed with new heads. You can remove the valve covers and clean thoroughly around the spark plug tubes with a solvent at the tube insertion point in the head and then force an oil resistant sealant (RTV Grey I believe) into the crevice around the perimeter that should cure the problem if done well.
Where can I find the TSB? I want to try it but I want to be positive I鈥檓 putting the RTV in the right location. Are there seals under the spark plug tubes that can be replaced?
 

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Where can I find the TSB? I want to try it but I want to be positive I鈥檓 putting the RTV in the right location. Are there seals under the spark plug tubes that can be replaced?
The TSB instructs to replace the heads, and they are to be marked for destruction to prevent rebuilding and reinstalling on another motor. The tubes are permanently installed in the cylinder heads and are not serviceable. The RTV application is a DIY work around for those who do not want to disassemble an otherwise normally working engine except for the oil contamination. You simply clean around the joint the tube is inserted into to aid adhesion and seal it.

I had the problem with two tubes and thought about it, but didn't go to the extent of applying a vacuum to the tube to help pull sealant into the crevice and instead forced it in and it worked wonderfully. This should help;

 
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