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2008 GMC Acadia 150,000 miles
On my way to work and the Check engine light, Stabilitrak, traction control, and a reduced power lights all came on in and engine was running really tough. The only code that was showing was a P0300. I replaced all the spark plugs, tested coils all tested good, but when I did a compression test there was no compression on the #3 Cylinder. All The other cylinders were right at 120 psi dry test. The engine will start right up but with a rough idle. I put oil in the #3 Cylinder and showed nothing on the compression gauge. From what I have found would this be a head issue? I have been doing some research but have found little on head problems. I know they are known for bad timing chains, but I don't think that the timing chain is the main issue due to it starting right up and running.
 

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Wonder if the engine's suffering from a bent, cracked, or burnt valve at that cylinder. :shrug:

:welcome: , BTW.
 

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Time to drop a diagnostic camera down the spark plug hole to get a visual. I would be leaning towards a burnt valve.
 

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divotdug said:
Time to drop a diagnostic camera down the spark plug hole to get a visual. ...
Pay attention to the valve seats, too.
 

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I thought I read about severe Carbon buildup causing low pressure readings.

Though this was on the DI models.. 2009+
 

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rbarrios said:
I thought I read about severe Carbon buildup causing low pressure readings.

Though this was on the DI models.. 2009+
I could understand that but the OP said he has no compression. Could be carbon buildup on a valve seat preventing a valve from closing. Should be easily diagnosed with a camera.
 

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divotdug said:
I could understand that but the OP said he has no compression. Could be carbon buildup on a valve seat preventing a valve from closing. Should be easily diagnosed with a camera.
its possible its all cruddy and not sealing I guess.... yup-- camera.
 

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Back when I was knowledgeable I would have said a stuck open valve. Primarily because it seemed to happen very quickly. Of course a broken valve would also happen quickly. Is that possible on modern engines?

George
 

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GeorgeC said:
... Is that possible on modern engines?
Probably is, but one would think damage to the engine from something like that would be immediate and severe. :shrug:
 

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2008 GMC Acadia 150,000 miles
On my way to work and the Check engine light, Stabilitrak, traction control, and a reduced power lights all came on in and engine was running really tough. The only code that was showing was a P0300. I replaced all the spark plugs, tested coils all tested good, but when I did a compression test there was no compression on the #3 Cylinder. All The other cylinders were right at 120 psi dry test. The engine will start right up but with a rough idle. I put oil in the #3 Cylinder and showed nothing on the compression gauge. From what I have found would this be a head issue? I have been doing some research but have found little on head problems. I know they are known for bad timing chains, but I don't think that the timing chain is the main issue due to it starting right up and running.
The SAME EXACT thing just happened to my car. 2013 Buick LaCrosse 3.6L. Do you happen to know what the issue was? I did regular oil changes and was working perfectly until it broke down in the middle of the road out of no where.
Thanks in advance
 
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