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2007 Silverado 6.0l (vortec Max - Nbs) Compression Test

ssabens

By ssabens
in Ask A GM Technician

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ssabens Enthusiast

ssabens

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Due to the dealer no longer performing real diagnostics, I decided to pull and change my spark plugs. Note: I understand why they don't want to do real diagnostic work, they would starve, as it doesn't pay; it's just really frustrating that I can't have the truck I thought that I bought.

 

I noticed a good amount of wet engine oil on the threads; so I decided to do a compression test.

 

To sum up the results, I have a range of 120psi to 135psi.

 

I also used a bore scope to take a few pictures of the pistons and valves, the number 7 piston has weird rusty looking (or bronze) spots, and the other weird thing I saw was the number 6 (I think) cylinder valve opening looked to be starting to "chip."

 

My main question is, what should the compression be in this engine?

I'm sick of the dealer telling me that there is nothing wrong with this thing. I can feel the thing "buck" or mis-fire on the highway with any bit of a load on the engine (meaning if I turn the AC on, it gets bad), not to mention when pulling my boat.

07VMax Enthusiast

07VMax

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Posted

does your truck have the knock when cold and a rough idle?? mine does and it bugs the crap out of me and the dealer says its normal they all do it

ssabens Enthusiast

ssabens

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does your truck have the knock when cold and a rough idle?? mine does and it bugs the crap out of me and the dealer says its normal they all do it

 

Well, it certainly does idle rough, not sure about the knock when cold. I did have a problem last year when it was raining or I went through a puddle. The dealer found a knock sensor code and tightened up the harness, seemed to do the trick.

 

The dealer says the rough idle is normal due to the engine needing to run lean, I hate it and the engine, but what can you do? Until they admit there is a HUGE problem with this engine, we're SOL.

Zembonez Senior Enthusiast

Zembonez

Posted
Posted

Your compression numbers are quite solid. If the engine has an actual miss, it will eventually trigger a stored code. Might not set the SES light, but could still be storing a code.

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