2012 Running Rough.
Thread Starter
Instructor
Joined: Feb 2021
Posts: 120
Likes: 13
2012 Running Rough.
Car has 5,600 miles. When I first start the car it runs rough. After it gets to running temperature, it smoothes out. Is this normal. My mechanic says they all do the same thing. 2012 Automatic. Thanks
Melting Slicks
Joined: Oct 2022
Posts: 3,330
Likes: 1,927
From: Ulta Vista, AZ
Can’t say mine runs rough, but there is a cold start enrichment table I guess to help get head temps up and all that jazz.
Every ice vehicle in existence to my knowledge does this. All your fluids are cold and needs to burn off I burnt gas.
Every ice vehicle in existence to my knowledge does this. All your fluids are cold and needs to burn off I burnt gas.
Melting Slicks
Joined: May 2020
Posts: 2,134
Likes: 1,305
From: North Little Rock, AR
I have an ‘06 and it does not run rough at startup. Could be a bad plug wire, coil pack, or spark plug.
I find it odd that a mechanic would say a rough idle is normal at startup.
I find it odd that a mechanic would say a rough idle is normal at startup.
Moderator, Tech Contributor
Joined: Sep 2013
Posts: 15,498
Likes: 3,999
From: Cape Coral, Florida
Your car shouldn’t be running rough until it gets up to operating temperature…if your mechanic has a scan tool and can interpret “live data” he should be able to see if something is wrong as the engine warms up…maybe find another mechanic…most know how to turn wrenches but very few know how to diagnose!!
Last edited by C5 Diag; Jul 4, 2023 at 10:34 AM.
Melting Slicks
Joined: Jul 2005
Posts: 2,649
Likes: 863
So my '12 also runs a little rough till it gets warm, and even when warm doesn't idle smoothly. The LS3 does have a fairly decent cam in it from the factory - I tend to think that's at least part of the issue. But - the car seems to do pretty well when I fully depress the accelerator, so I don't worry about it too much. I have been in other LS3 cars - and they also run a bit rough during warm up.
Instructor
Joined: Jun 2021
Posts: 228
Likes: 95
From: Westminster, Maryland
I had this problem shortly after I got my ‘11 GS two years ago with only 7200 miles. When tuning my LS3, my tuner/mechanic replaced both spark plugs and wires that were faulty. I suspect that the plugs’ premature wear was due to the original owner taking the car mostly for three mile trips between his home and shop! The GS actually starts better, although still less rough, ever since I ran it in an autocross last year. The LS3 cars are meant to be driven and revved from time to time!
