2018 Silverado 6.0 Idle Stumble

[CKN]

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.

I unfortunately had the same issue with a used 2012 GMC SLT that I bought that was a "certified" vehicle at the GMC Dealer. It had a 5.3. Sometimes it would idle like a lumber truck. Chased the problem for almost a year with no results. The only up side is when I traded it in on the new 2018 Silverado they gave me $5,000.00 less than what I paid-in short it cost me the same amount as a lease would have. BTW-it's not normal.

I agree...if you can afford to do so...dump it. This is a issue that is very, very difficult to diagnose and repair.

 

[DriveHard]

And this is the problem with computer diagnostics. If it does not set a code the dealer does not want to deal with it even though there are a ton of sensor read outs that will tell you if something is going wrong. But you have to know what the normal reading should be and how to run the tests which is either beyond most techs or not profitable.
I have a similar problem with my 2015 3500 Express. Occasionally I get a slow start where I turn the key and it takes a few sec before the engine starts to crank and then everything goes back to normal the next 50 starts. I always go to ON for a sec or 2 to let the fuel pump run before going to start but it does not help and the dealer tells me the same thing, No Code No Problem. And I also have the rough Idle for 30 or 40 sec on cold starts.

This is a relay issue...I had the same issue, and it finally got to the point I would turn the key to start, and nothing would happen. Cheap and easy fix.

 

[samven]

This is a relay issue...I had the same issue, and it finally got to the point I would turn the key to start, and nothing would happen. Cheap and easy fix.

Thanks, I will check that. You would not happen to know if it was a relay under the hood or under the seat.

 

[odotb]

I had somewhat of the same issue, turned out to be an over oiled aftermarket air filter.

 

[DriveHard]

Thanks, I will check that. You would not happen to know if it was a relay under the hood or under the seat.

Its a relay under the hood. When I got stranded, I used the headlight relay to get me going again.

 

[samven]

Its a relay under the hood. When I got stranded, I used the headlight relay to get me going again.

Thank You, that really helps. I will go out today and get the part # on order.

 

[Silver]

Check for vacuum leaks at a poorly connected junction or gasket. Clean MAF sensor.

 

[ls1mike]

It's something that would be hard to capture on video, really. I'm running Shell or Sunoco 87 Octane fuel. No, I haven't tried ECU reset.
I had the GM dealer scan for codes, and they saw nothing.

Like I mentioned before, in the morning, she just stumbles a bit at start up....maybe 30 seconds or so. You can feel it as you put it in gear and move the truck. It is NOT bucking and jumping around, but you can definitely feel it. Kinda similar when you start up an older piece of power equipment (like a garden tractor or even a weed eater....you have to let it warm up a minute before it's really going to run smooth.

I've tried to get it to "stall"...but it won't. If I give it a decent amount of fuel right at start up, it hesitates and grumpily begins to accelerate....and of course, smooths out very quickly.

Reset ECM, run some good stuff throught it I bet it clears up.

 

[ls1mike]

Direct injection? If so, welcome to the GM truck misfire club!

However if your engine is just a regular port injected, no cylinder deactivation engine. You’re good! That’s just the good old GM stumble bumble.

6.0/6L90E, nothing like the half ton, not direct injected, no 6L80E or 8 speed problems, no thermostat in the transmission so they run cool, No AFM. Solid pretty much old LS based technology. My 17 has no stumble, at least if it does I have not noticed it.