C7 idling question
Thread Starter
Race Director
Joined: Apr 2007
Posts: 16,023
Likes: 1,645
From: Toronto, Canada
C7 of the Year - Unmodified Finalist 2021
I got news dude, warranty or not, going into a dealer and saying "my tach fluctuates a little at idle" and expecting some sort of warranty repair would be like expecting Bernie Sanders and AOC
to co-sponsor a fiscal policy bill that actually makes a shred of sense and has a glimmer of hope of being sustainable
to co-sponsor a fiscal policy bill that actually makes a shred of sense and has a glimmer of hope of being sustainable
Thread Starter
Race Director
Joined: Apr 2007
Posts: 16,023
Likes: 1,645
From: Toronto, Canada
C7 of the Year - Unmodified Finalist 2021
Plug a scanner into it and see what the ECM says the RPM is. So if you see it running between say 1000 and 1500, you have a problem. OTOH if it is between 1000 and 1050, you are within norms. It will never stay at a certain RPM so there will be fluctuations. What we are trying to see is if there is a lot of difference or a smaller difference.
Team Owner
Joined: Sep 2010
Posts: 32,042
Likes: 4,610
the lump idle is a feature not a bug, it is a call back to the lumpy cams of yesteryear. slight fluctuations in the idle like you describe is probably normal. I would live with it until it causes a problem or take it to a dealer have them do the diagnostics and pay 175 bucks( in the past my dealer has waived that but I have been bringing both of my corvettes to them for 10years)
Team Owner
Joined: Sep 2000
Posts: 25,009
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From: Far NW 'burbs of Chicago
St. Jude Donor '13
I got news dude, warranty or not, going into a dealer and saying "my tach fluctuates a little at idle" and expecting some sort of warranty repair would be like expecting Bernie Sanders and AOC
to co-sponsor a fiscal policy bill that actually makes a shred of sense and has a glimmer of hope of being sustainable
to co-sponsor a fiscal policy bill that actually makes a shred of sense and has a glimmer of hope of being sustainable
Our local dealer Corvette tech would certainly spend a few minutes checking it out.
You can throw them a bone by having them do some other work (oil change?) that they will definitely get paid for, if it's due.
As others have pointed out; the smoothness of the idle on the same car varies somewhat depending on whether the engine is fully warmed up, A/C load, and phase of the moon.
1/4 mile/AutoX
Joined: Jun 2014
Posts: 11,441
Likes: 2,186
From: Buffalo Texas
if the engine is not moving or rocking it's smooth 
all our Vettes are manuals, maybe the auto's are more sensitive ???? my 2006 Silverado with close to 300k is also smooth ????
all our Vettes are manuals, maybe the auto's are more sensitive ???? my 2006 Silverado with close to 300k is also smooth ????
Team Owner
Joined: Sep 2010
Posts: 32,042
Likes: 4,610
When "under-load," @ idle the engine is torqued, if in gear against the automatic transmission.
M7 engines have no-load against the engine to keep it from it's rocking motion of the vehicle @ idle.
Very perceptive.👍
Last edited by Skid Row Joe; Mar 21, 2022 at 09:10 PM.
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Team Owner
Joined: Jul 2004
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From: Hartford WI
Team Owner
Joined: Jul 2004
Posts: 28,432
Likes: 3,285
From: Hartford WI
Shouldn't the idle be checked with the transmission in neutral be it manual or automatic?
Instructor
Joined: Dec 2021
Posts: 118
Likes: 42
Odd. A shaking hood and vibration at idle is one of the first things I noticed about my 2019 Stingray. My tach also varies quite a lot especially before warm up. Its my first Corvette. I was told this was normal however I sat in another C7 ( 2017 I believe) which was smooth and didn't have that hood shake and vibration. I also drove my son's C5 which was very smooth. My car seems fine, other than the electrical gremlins so I just go with it.
