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Ask GM Tech (Cam) Your Own Question
GM Tech (Cam)
GM Tech (Cam), Chevy Technician
Category: Chevy
Satisfied Customers: 29520
Experience:  GM Grand Master Technician 2007. 14 years experience.
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2003 gmc envoy: cyl..used to have engine vibration..once engine warmed

Resolved Question:

2003 gmc envoy 160,000 6 cyl. used to have engine vibration and would stop once engine warmed up now much worse it doesn't go completely away when warmed up. Can feel it in the fenders. use mobile 1 and change on time. all plugs are tan compression is 150psi, removed serpentine belt so no ancillary components would affect engine no difference. Vibration is with vehicle not moving. in drive its worse in park its less. Damper appears to be intact its hard to see down there, grabbed it and tried to feel if it would slip if I turned it left and right but no movement was felt. Don't know if timing is done with timing light on damper if so I can check to see if Tmarks have moved. What am I missing???
Submitted: 8 years ago.
Category: Chevy
Expert:  GM Tech (Cam) replied 8 years ago.
Welcome Redcast. I would perform a cylinder leakage test. These heads have had issues with the valves not sealing properly. Is the check engine light on?
Customer: replied 8 years ago.
OK I need a little more info. Although I have done compression tests before, what is the correct procedure to do a leak down test and if It shows valve leakage how much would it take to cause extreme vibration. Have had vehicles before with bad valves and they didn't idle well unless rpm was set higher this is not the case here as the idle is fine at regular rpm. The check engine light is always on. The error code says it is because engine temp isn't high enough. I haven't checked for new codes as I have to take it to the local auto parts store to do that and didn't want to drive it there. Could excessive carbon be some of the problem as the spark plugs have a black carbon coat on the round part of the plug that is the screw in part or rather where the threads begin part of the plug but the electrodes are tan.
Expert:  GM Tech (Cam) replied 8 years ago.
The carbon could be causing the issue. Have you ever replaced the plugs?
Customer: replied 8 years ago.
Platinum fours 20,000 miles ago. Can u suggest a good de-carboner
Expert:  GM Tech (Cam) replied 8 years ago.
I was under the impression that you had not changed the plugs. Now that you have told me the type, I am convinced you need new plugs. The Bosch plugs especially the Platinum 4 are bad for causing misfires. Put a set of AC Delco plugs in and see what happens.
Customer: replied 8 years ago.
OK I will try that. If I need more help after that how can I locate you?
Expert:  GM Tech (Cam) replied 8 years ago.
After you click accept you can reply to this post and I will continue to assist you on this issue. For future questions, in the first line type For Blue Gorilla to answer and it will be left for me.
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