2017 Denali fluttering when accelerating. VIDEO

[denali17gmc]

Picked up a 2017 Denali just over a month ago, been hearing a "fluttering"/rattling type sound when accelerating. I'd say it usually happens at about 1500-1700 RPM... occurs when you're asking for a little more speed and usually stops when at cruising speed.

Dealer said it's the sound of some exhaust valve with the purpose of keeping the muffler quiet... is this normal? Seems too loud to be normal. Video attached.

 

[thavngr98]

I have the same problem on my XL. I think its an exhaust leak. Going to the dealer next week. See what happens

 

[denali17gmc]

I have the same problem on my XL. I think its an exhaust leak. Going to the dealer next week. See what happens

That's what I was told when I took it in for service. They changed the entire exhaust and the issue still persist...

 

[denali17gmc]

That's what I was told when I took it in for service. They changed the entire exhaust and the issue still persist...

Please keep me posted on what they say.

 

[thavngr98]

Please keep me posted on what they say.

will do!

 

[MikeW]

I am having similar issue - but its on a 2002 with 278K.. thought it might be transmission going.... please keep us informed!

 

[Fred Bickley]

Can't really tell from your video, but if it is a shudder, it could be the torque converter. I just had my 2016 Denali in and they replaced it fixing the issue. I had a shudder at the gear changes that happened between 1200 to 1900 RPMs on gears 3 through 6. There is also a software update that might be necessary as well.

 

[jeffbco]

GM is aware of the issue -

http://sandyblogs.com/techlink/?p=3296

 

[Tacky]

I believe you are hearing characteristic noise that comes in with V4 engine operation. The valve in the exhaust is intended to minimize it. I don't believe there is anything that will eliminate it in the long term. I have seen several exhaust systems replaced for this but the noise comes back.

 

[Nashoba]

I assume you have cylinder displacement down to V4 and you know about the flapper valve that a lot of folks complain about. We have V8 to V4 on our 2008 Tahoe Hybrid and my wife was complaining of the same stumbling the other day. So, I did an Oklahoma quick tune up on the vehicle. I got it up to operating temp and then performed several 60 to 90 mph runs in quick succession. Then I let everything sorta cool down to normal, although the temp gauge never moved up, and them performed several 20 to 98 mph (darn engine electronic governor) runs to continue the "tune up". When I got back to town and drove through town so I would have to stop at lights and stop sighs, I noticed no stumbling or hesitation at all. I was even able to climb a steep hill on electric motor only on the way to the house. That is the first time I'd been able to ever do that. The Tahoe is my wife's vehicle and she is a very "gentle" driver and hardly ever hits passing gear so it can get clogged up. I also put a half can of Berryman's B12 Chemtool in the gas tank which was about a quarter full before the "tune up". After I got through, I put a full can in the tank and filled it up with no ethanol fuel regular. I will add another can and a half of Berryman's to the tank the next fill up. A can treats 20 gallons of fuel. Sometimes you just gotta blow the soot out of them. But you have to find a safe stretch of road to do it!

 

[denali17gmc]

Thanks everyone for your input/ideas!
So i went and did that bolt "hack" on the valve and it didn't really seen to do anything about the noise I'm hearing...
This is after having the entire exhaust swapped out by the dealer a few weeks ago. They said it was the valve making the noise and this was normal for these trucks, although I've test driven 3 other 2017 denalis and couldn't replicate the sound.
I have a service appointment at a different dealer this Wednesday, not too optimistic at this point but I'll keep you all posted.

 

[thavngr98]

Please keep me posted on what they say.

I pick my truck back up this morning. For mine they found 2 exhaust leaks one on clamp weld at Cat and one on the hanger weld of the muffler. They had to order me a whole new exhaust system. Hope this helps...

 

[denali17gmc]

I pick my truck back up this morning. For mine they found 2 exhaust leaks one on clamp weld at Cat and one on the hanger weld of the muffler. They had to order me a whole new exhaust system. Hope this helps...

Took mine to a different service center this morning. They didn't want to deal with it... claimed I had to take it back to the original servicing dealer since they already started to look at the issue. BS...

So your issue all gone then thavngr98?

 

[thavngr98]

Took mine to a different service center this morning. They didn't want to deal with it... claimed I had to take it back to the original servicing dealer since they already started to look at the issue. BS...

So your issue all gone then thavngr98?

Not yet they had to order the exhaust system. Said it would be in next week. Ill keep you updated...

 

[thavngr98]

I had my exhaust replaced today and I no longer have the sound.

 

[DenaliDrivinDad]

Mine does this, and the range at which it rattles has grown. I also tested the flapper valve early on with no improvement. Checkout 27 seconds in this video.

Shortly after this, the dealership claims they just replaced the VLOM, the fuel lines including the fuel feed pipe mentioned in PIP5395A, and the high pressure fuel pump. They also claim to have checked the pushrods. The noise is still there for me. I'm at 9200 miles now.

My Denali is one of the noisiest vehicles I've owned.

 

[denali17gmc]

Mine was at the dealer all last week, they replaced a belt that was showing uneven wear... it did not solve the problem.

Took the truck back in on Tuesday but still haven't heard anything from them.

Mine makes this "clicking"/"fast flapping" kind of noise at low speeds and at highways speeds it can turn into a squeaking kind of whistle. The pitch it can hit is really bothersome. I know they think I may be exaggerating but there is no way this is normal...

 

[denali17gmc]

This is so strange to me... can't believe they consider this normal. It's really is extremely annoying especially because I spend much of my car travel time during the week returning work phone calls. I can hear the sound fluctuating as I adjust the gas pedal. Frustrating.

I believe you are hearing characteristic noise that comes in with V4 engine operation. The valve in the exhaust is intended to minimize it. I don't believe there is anything that will eliminate it in the long term. I have seen several exhaust systems replaced for this but the noise comes back.

 

[denali17gmc]

Mine does this, and the range at which it rattles has grown. I also tested the flapper valve early on with no improvement. Checkout 27 seconds in this video.

Shortly after this, the dealership claims they just replaced the VLOM, the fuel lines including the fuel feed pipe mentioned in PIP5395A, and the high pressure fuel pump. They also claim to have checked the pushrods. The noise is still there for me. I'm at 9200 miles now.

My Denali is one of the noisiest vehicles I've owned.

I'm regretting my purchase. Some may say it's a minimal sound I'm getting but I expect a reasonably quiet ride from a vehicle with this price tag.

 

[jeffbco]

I'm regretting my purchase. Some may say it's a minimal sound I'm getting but I expect a reasonably quiet ride from a vehicle with this price tag.

Does the noise change/go away if you turn off AFM. You can effectively do this by selecting "L" in the transmission, advance the gear using the toggle to 7 on the gear shift lever and you'll remain in V8 mode until you shift to 8 - car will shift normally through gears 1 - 7 set this way. At least you'll be able to tell if it's a V4/V8 issue. Good luck.