2018 Silverado 6.0 Idle Stumble

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2018 Silverado 3500HD with 6.0L gas motor. I notice in the morning when I start my truck, the idle stumbles moderately. As I back up out of the driveway, it stumbles as well as I pull way down the road. It immediately goes away once I get the RPM's up and is hardly noticable once warmed up and back in park. The truck has never had a "sewing machine" idle. It's always felt a bit "rough". The tach has a small bounce to it (tiny), but you can feel it in the seat.... Even when fully warmed up. Any ideas??
 
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It's funny because my 2018 Elantra used to behave similarly. Turned out to be a bad coil, taken care of under warranty. Not saying that's your problem, too, as many things can cause a lumpy idle. Are you still under warranty?
 
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Yes, still under warranty. No CEL. I always get good gas, it has done this for 2 years, 45k miles
 

JTK

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Buffalo, NY
It would be interesting to do some data trends on it to see if it is misfiring at idle. Apparently it's not enough to light the CEL. Could be nothing.
 
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The ATL
Why even speculate or worry about it. Take it to the dealer since it's under warranty and let them diagnose and repair it. Make sure you tell them it stumbles the worst in the morning when cold.
 
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Originally Posted by JTK
It would be interesting to do some data trends on it to see if it is misfiring at idle. Apparently it's not enough to light the CEL. Could be nothing.
Nothing? If it won't idle correctly it has a problem.
 
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Originally Posted by PowerSurge
Why even speculate or worry about it. Take it to the dealer since it's under warranty and let them diagnose and repair it. Make sure you tell them it stumbles the worst in the morning when cold.
I've tried it. Two differrent dealerships basically said, "We've had a few people mention this. We've looked into it. There's no CEL." I guess I could take the truck to a "tune shop" and have them obtain some data. Perhaps some fuel tables need adjusted. Anyone have any other ideas?
 
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1/2 hr N.E. of Detroit
Originally Posted by Phishin
2018 Silverado 3500HD with 6.0L gas motor. I notice in the morning when I start my truck, the idle stumbles moderately. As I back up out of the driveway, it stumbles as well as I pull way down the road. It immediately goes away once I get the RPM's up and is hardly noticable once warmed up and back in park. The truck has never had a "sewing machine" idle. It's always felt a bit "rough". The tach has a small bounce to it (tiny), but you can feel it in the seat.... Even when fully warmed up. Any ideas??
If they can't locate the problem and it bugs you every day, trade the vehicle or sell it. I once had a new early 70s Ford Econo Van that had loose steering that drifted, direction depended on road slant. Never got fixed despite complaints by me. By the time it was a year old, I got fed up and traded-it-in. Never bought another Ford again. My first car-ever, in 1969, was a Ford. That was a bad decision purchase. Me and Fords don't get along.
 
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4WD

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Texas
Tried a strong dose of PEA based fuel system cleaner … ? Two bottles of Gumout Regane just cured rough idle in my 5.3L
 
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Indiana
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Originally Posted by 4WD
Tried a strong dose of PEA based fuel system cleaner … ? Two bottles of Gumout Regane just cured rough idle in my 5.3L
Yep. I've run 2x doses for 2 full tanks. I've also run a few tanks of E85 through it. (It's a Flex Fuel compatible 6.0L)
 

4WD

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13,121
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Texas
Lot of parts houses can plug in and look for codes that will not always trigger a CEL on the dash. Free service.
 
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