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Ask Gary Your Own Question
Gary, ASE Certified Technician
Category: GMC
Satisfied Customers: 16766
Experience:  GCM master tech over 25 years
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2003 Envoy inline 6 idle rough when stopped no check engine

Customer Question

2003 Envoy inline 6 idle rough when stopped no check engine light. After it runs for a while its alright.
Submitted: 2 years ago.
Category: GMC
Expert:  Gary replied 2 years ago.
Welcome! My name is ***** ***** I will do my best to assist you with this problem.
I am sorry for the long wait
is it just a rough idle where if you put your foot on the gas pedal a tiny bit it will idle good ?
driving it the truck is fine ?
Customer: replied 2 years ago.
Gary, after Envoy has sit for several hours like at night or work when I stop at a stop sign it has a vibration. After about 20 minutes it smoothes out.
Expert:  Gary replied 2 years ago.
any access to a scan tool to see live computer data ?
how old are the spark plugs ?
how old is the fuel filter ?
how long since you had a fuel injector service ?
Customer: replied 2 years ago.
My mechanic has tool, but with no check engine he's stumped. Envoy has 78000 miles. I've cleaned the throttle body. Never had ejector service or plugs. Fuel filter new after fuel pump change.
Expert:  Gary replied 2 years ago.
can this be driven and when its acting up monitoring current and history misfires on the misfire data list which cylinder are showing a misfire ? are any ?
Customer: replied 2 years ago.
The truck can be driven. As far as the other stuff I don't know, I'm not a mechanic. Is it possible it needs the computer up dsted??
Expert:  Gary replied 2 years ago.
very rare for any updated programming will correct this problem
usually when they will shake at idle at a stop there is either an idle way too low or a misfire happening
if this is possibly a more so low idle issue then yes updated computer programming can usually correct that issue especially if the throttle body has already been cleaned
with no codes the best action is to update the programming if it still does this the truck needs to be driven with it acting up with a scan tool and see when its acting up is nay cylinders are showing a misfire or not which could be as simple as spark plugs or cleaning the injectors
Customer: replied 2 years ago.
I was hoping with as many people complaining of same condition on Internet that it would be something that could be easily fixed without changing motor mounts, Trans mounts, cam positioning sensor, ect. Ect
Expert:  Gary replied 2 years ago.
tough to say right now since any mount issue would not go away when warm
and a timing chain or cam sensor issue would be setting codes
yes there were many issues with these engines but with it going away warm eliminates a mount issue and with NO codes set it should not be a cam sensor or timing chain issue as that would set codes for those kind of issues
with no codes that is the direction you need to go next without guessing and throwing parts at this truck
1 problem 1 fix
Customer: replied 2 years ago.
So what did my 24 bucks get me. What are you suggesting. I can't believe this can't be sorted out.
Expert:  Gary replied 2 years ago.
of course it can be sorted out but right now you do not know if this is an engine issue or not yet
this truck has not even been diagnosed yet correctly
lets see if any other experts have any ideas
hand on another expert will reply back to you
Customer: replied 2 years ago.
Gary, let me say it's more of a vibration than a rough idle, the rpm at idle is at 600. It just sounds like a strong vibration.