Shaking like a 70's car at a stop light.

[jpmiami]

Just picked up my brand new 2015 Sierra Denali....truck fluctuates like crazy at idle (2-300 rpm's).....called the dealer and service said it was normal for GMC's and has been a problem.....not sure what to do....

they said the same thing to me (they all do that)

[jpmiami]

2014 Sierra Denali 23k miles and every-time you stop at a light RPM'S drop a little below 500 and it starts doing the shake! Anyone with this same issue? 3 dealers and response is they are all like that? contacted GMC and no help at all, premium fuel and nothing.

 

Time to change the truck i guess.

 

So got a call from the dealer to bring the truck in to do the engine mount shims bulletin, don't know how this is going to fix the RPM issues but lets see.

[baddaddition]

Spray the dang maf sensor with the proper cleaner and clean your air filter. They are temperamental wh***s. It'll go away.

 

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[baddaddition]

A small amount of crude or hair strand can make em idle crazy. Tunes are a plus! Lol haven't had many gassers in some years, but run a 750hp Duramax... She's has a temper problem from time to time, however EFI Live makes it a whole new world! Or a tech 2

 

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[hamd1719]

Yes engines are grounded to the frame. But they have bushings that go on the motor mounts to reduce vibration and to ensure that its not metal on metal. Mine simply did not have enough support on one side of my motor so the technician installed shims to make my engine sit level and reduce felt vibration.

Did the shaking completely go away?

 

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[hamd1719]

There is a bulletin on this condition, has anyone tried it and does it eliminate the rough idle condition http://sandyblogs.com/techlink/?p=3780

 

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[jpmiami]

Well got the truck back after dealer installed 3 mm thick shims between bottom surface of engine mounts and frame bracket on the inboard side of mount, Well vibration still there.

 

Yesterday i drove my friends 2008 Yukon XL and did not feel any vibration at all! and it has 125k miles. GM has been very wiling to help so far and dealer also, lets see.

[tootall87]

Took mine in for it's first oil change and told the service adviser about my vibration. He remarked that, "thats normal and they all do it." I then brought out my guns and showed him some notices about the motor mount shims and the rear end assembly. He said they'd take a look at it...

 

Dropped it off this morning for a couple of days I assume. Said they would take care of me. We'll see as this is my first warranty claim on any vehicle ever. Got a loaner silverado and guess what, no idle vibration hmmmm.... thought they all did it....

[jpmiami]

Took mine in for it's first oil change and told the service adviser about my vibration. He remarked that, "thats normal and they all do it." I then brought out my guns and showed him some notices about the motor mount shims and the rear end assembly. He said they'd take a look at it...

 

Dropped it off this morning for a couple of days I assume. Said they would take care of me. We'll see as this is my first warranty claim on any vehicle ever. Got a loaner silverado and guess what, no idle vibration hmmmm.... thought they all did it....

Good to know, I haven't heard anything back from the dealer or GM on this issue.

[taylorcam11]

Did the shaking completely go away?

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Yes the shims worked on mine! I can no longer feel the vibration. Only thing im not crazy about is that i would like to know why the engine vibrates in the first place? GM is not fixing our trucks they are simply making it where you cant feel the vibration any more.

[ghgmi]

Only thing im not crazy about is that i would like to know why the engine vibrates in the first place?

 

Is the vibration in 4-cylinder mode? Four-cylinder engines can't be perfectly balanced due to second-order effects that I don't really understand, but have occasionally read about. The bigger the engine (and a 5.3L / 2 = 2.7L four is a big four), the worse the vibration. Since it's due to second-order effects, the other four non-firing pistons don't help the balance. Big straight four engines use balance shafts spinning at twice the crankshaft speed to counter-act the effect, but I doubt the V8s have those.

[Dropsix]

 

Is the vibration in 4-cylinder mode? Four-cylinder engines can't be perfectly balanced due to second-order effects that I don't really understand, but have occasionally read about. The bigger the engine (and a 5.3L / 2 = 2.7L four is a big four), the worse the vibration. Since it's due to second-order effects, the other four non-firing pistons don't help the balance. Big straight four engines use balance shafts spinning at twice the crankshaft speed to counter-act the effect, but I doubt the V8s have those.

 

It's at idle. The trucks don't sit in 4 Cylinder mode at idle.

[tootall87]

Update: service manager agrees it's an issue that needs fixing. 1st up is shimming the motor mounts. If they're not satisfied that the vibration is gone they are going to replace the motor mounts completely.

 

Another couple days. I'll take it.

[jpmiami]

Update: service manager agrees it's an issue that needs fixing. 1st up is shimming the motor mounts. If they're not satisfied that the vibration is gone they are going to replace the motor mounts completely.

 

Another couple days. I'll take it.

 

They just did that to mine and nothing changed, sent service advisor a video of the tach going up and downs from 500 to 450 at a stop light and keeps saying thats normal? GM has desapered on me after trying to help out at the begining.

[tootall87]

I got mine back from the dealer on Monday. Waited a bit so I could drive it a couple times. They shimmed the right motor mount. Paperwork doesn't say how much they shimmed.

 

Idle vibration gone. Guess I'm one of the lucky ones.