Brand new 2021 Denali shuddering

[Segalldontfly]

First, I want to say I did not join the forum to complain. I have had my 2021 Yukon Denali for a week and I love everything about it so far.

I am noticing a slightly rough idle. I don’t even know I would call it rough. Very slight rpm fluctuations and a couple faint shudders. I have a September 2021 build date which made me more confident in the purchase. I don’t know if I am being paranoid or should be concerned. Has anyone else experienced this and is it normal? I am still on my first tank of dealer gas and have about half a tank to go until empty. 185 miles on the ODO.

Is it too soon to bring into the dealer for service to take a look?


Any advice appreciated.

 

[Micahsd]

Looks like a nice ride. I do prefer the GMC look over the Chevrolet in the front.

My ‘21 Tahoe does the same thing at idle. I suspect it’s the dynamic fuel management or something kicking in on mine although yours might not have that due to the chip shortage.

When driving up small hills and such I’ll feel it shudder a little as if it’s stuck in too high if a gear but doesn’t want to change. Of course if I give it more power, then it will downshift. Not sure if that’s the shudder you’re describing, but if it is there’s another thread on here which makes it sound pretty typical due to the programming.

 

[Segalldontfly]

Looks like a nice ride. I do prefer the GMC look over the Chevrolet in the front.

My ‘21 Tahoe does the same thing at idle. I suspect it’s the dynamic fuel management or something kicking in on mine although yours might not have that due to the chip shortage.

When driving up small hills and such I’ll feel it shudder a little as if it’s stuck in too high if a gear but doesn’t want to change. Of course if I give it more power, then it will downshift. Not sure if that’s the shudder you’re describing, but if it is there’s another thread on here which makes it sound pretty typical due to the programming.

Thank you! Good to know. How many miles do you have on your Tahoe?

I think I am going to try and get past the 500 mile break in (per owners manual) and a fresh tank of premium to see if any improvements.

I have dfm but no auto stop/start.

Appreciate the insight.

 

[Micahsd]

Thank you! Good to know. How many miles do you have on your Tahoe?

I think I am going to try and get past the 500 mile break in (per owners manual) and a fresh tank of premium to see if any improvements.

I have dfm but no auto stop/start.

Appreciate the insight.

Mine was built on March 19th and so far I’ve got 5,500 miles on it. Love the vehicle.

I’m jealous that you don’t have auto start/stop. I have to hit a button each time to disable it!

 

[SSGUNNER]

Wow that is a stunning ride!!! Is that black? Loving the tire/wheel combo from factory.

I think I’ve noticed similar shudder or slight rough idle. I read somewhere on the web that it could be due to having auto start stop off. At least after reading that for me that could be a culprit but being you don’t have auto stop may not be the case.

I honestly don’t feel that as much or at least don’t pay attention . My RST is a May 21 build date and just broke 5902 on mine. One thing I noticed I did from the beginning was a lot of idle not intentionally but more so the situation I was in. I also remember reading something about high idle’ing may be good for these engines but again can’t remember where. It must of been on some Silverado forum as these engines are similar if not identical.

Lastly (again don’t remember) but I want to say while watching a vid on YouTube about the lifter tear down on these 21’s I stumbled across another tear down believe it was for a Silverado where in the vid they showed where the AFM or DFM connection is right underneath the center engine cover (black piece) and disconnecting it would shut off the afm/dfm crap. Can’t recall if it talked about getting a CEL tho.

Anyways nice rig man, enjoy it hopefully it’s nothing. I can’t get enough of mine and always get stares lol.

 

[cdgtahoe]

My Yukon was built June 2020 and at first it had a high idle when hot. Rough idle was not often. Now that I have 13700 miles. New engines do not idle smooth because of have to run lean at idle. Change your oil early first few times. I did my first 3000 miles and second with 4000 miles

 

[Segalldontfly]

Wow that is a stunning ride!!! Is that black? Loving the tire/wheel combo from factory.

I think I’ve noticed similar shudder or slight rough idle. I read somewhere on the web that it could be due to having auto start stop off. At least after reading that for me that could be a culprit but being you don’t have auto stop may not be the case.

I honestly don’t feel that as much or at least don’t pay attention . My RST is a May 21 build date and just broke 5902 on mine. One thing I noticed I did from the beginning was a lot of idle not intentionally but more so the situation I was in. I also remember reading something about high idle’ing may be good for these engines but again can’t remember where. It must of been on some Silverado forum as these engines are similar if not identical.

Lastly (again don’t remember) but I want to say while watching a vid on YouTube about the lifter tear down on these 21’s I stumbled across another tear down believe it was for a Silverado where in the vid they showed where the AFM or DFM connection is right underneath the center engine cover (black piece) and disconnecting it would shut off the afm/dfm crap. Can’t recall if it talked about getting a CEL tho.

Anyways nice rig man, enjoy it hopefully it’s nothing. I can’t get enough of mine and always get stares lol.

Yes it is black - thanks, I can’t help staring out the window at her myself.

Going to enjoy it until there is a good reason to be concerned, but may call the dealer for insight before going in as well.

I am not one to try and shut off the DFM until there is a known, reliable method (hopefully range gets a 2021 model working).

Going to try and drive a few hundred miles this weekend and will post any updates.

 

[Segalldontfly]

My Yukon was built June 2020 and at first it had a high idle when hot. Rough idle was not often. Now that I have 13700 miles. New engines do not idle smooth because of have to run lean at idle. Change your oil early first few times. I did my first 3000 miles and second with 4000 miles

Good to know, thanks. What I am describing is a slight fluctuation in rpm (+\- 50) from time to time. It’s very minimal but noticeable. I have other vehicles that behave similarly but I may be hypersensitive in this situation. Not sure but will continue to drive, enjoy and monitor.

 

[OR VietVet]

Welcome to the forum and nice ride indeed.

 

[Segalldontfly]

So I just found this video on YouTube.

If you watch at the 59 sec mark, the RPMs slightly waiver a bit after start up. This is exactly how my truck behaves.

Hope this is a helpful example. Seeing it on another vehicle makes me feel it is normal and nothing to worry about, but I would be interested in the opinions of others as well. Last time I regularly drove a brand new car was 4-5 years ago and this Denali has a lot more tech than anything I have ever owned.

Thank you to everyone who responded so far, this is a great community.

 

[Mike Diaferio]

I am not sure what all are talking about when it comes to rough idle. My 21 Denali was built in September 2020 and I now am just south of 18,000 miles. I have never experienced a rough idle at any time. I have never experienced a new engine running rough because they have to run lean! They are designed to run on the fuel they are expected to use. n the case of the Denali 6.2, you should be running premium fuel.

 

[cdgtahoe]

I have been running 93 octane fuel the whole time.

 

[Terry Hurlburt]

I have two Denalis, a 2014 and a 2018. Both with the 6.2 liter engine. Both engines have a slight “lope” to the idle that seems to be normal for this engine. I have asked the question at two different dealers and both said it was normal.
Interestingly the 2014 has had a super charger installed, bigger injectors to run E85, cat back exhaust and a custom tune to make max power. It still has the slight “lope” at idle.
Both vehicles have around 40000 miles now and seem to be doing just fine with routine maintenance.
Both are run on 93 octane regularly and of course E85 when I can get it.

 

[ddivinia]

Our 2022 Z71 tahoe doesn’t have auto stop. They paid me $50 since it didn’t have it. Heck, they should make it optional for people to delete that “featire“ for sure.

d.

 

[Quark]

Dealerships are known for putting the cheapest gas they can find in your new car. Next fill up use a top tier brand of gasoline and run it like you mean it.

 

[killjoy]

FWIW, my '21 AT4 is at the dealer getting all 16 lifters replaced. IME, the rough idle was very noticeable at stop lights... meaning you coast up to the light and stop, and the engine is trembling to the point it sounds/feels like it's going to stall. Tach blipping down below 300 RPM at idle, them blipping back to normal, then back down... like every second or two.

On mine, I think it was a exhaust lifter that went out, since it sounded like a popcorn popper under the hood. Cylinder was filling with gas/oil, then exploding into the exhaust manifold. Mine was may more than a typical lifter tap which is fairly quiet... this sounded like an exploding firecracker every second or two coming from directly under the intake manifold. Popcorn popper is the best description I give you. There was no debate/denying something wasn't right.... lol.

 

[JayBaywatch]

Hey there. I have a brand new 2023 Yukon Denali XL and I am experiencing what sounds like the same thing. I have about 1,500 miles on it and it just started happening today.

Did you ever figure out what it was?