Rough Idle = New Motor Mounts?

[Justin101714]

I just picked up my 2018 slt 6.2. See signature for details. Had a rough idle since I left dealer. Runs excellent otherwise. Currently have 1800 miles and 40 hrs on engine. Ran a few tanks of premium. Still get the chug that shakes seat at idle.

Give more time for brake-in? Time to contact dealer? Is it better to print TSB if so what’s the number of just show and tell?

Also been reading about a bad head casting? My truck was built 12/7/17. Hopefully missed that but just checked all fluids and all are normal but coolant overfilled.



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Is this consistent rough idle? Would you say it does it a few times within 5 seconds? A lot of the complaints I see aren’t any type of rhythmic rough idle, they are simply an operating characteristic of a V8. A lot of people started complaining of this when the 2007 body style emerged, all the way into the late 2013 models with the 5.3. Since Your truck is so new, give it some time. Now, if you’re at a stop light and it’s unbearable, like most with the problem are, then it’s not normal.


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[2018GMC]

Is this consistent rough idle? Would you say it does it a few times within 5 seconds? A lot of the complaints I see aren’t any type of rhythmic rough idle, they are simply an operating characteristic of a V8. A lot of people started complaining of this when the 2007 body style emerged, all the way into the late 2013 models with the 5.3. Since Your truck is so new, give it some time. Now, if you’re at a stop light and it’s unbearable, like most with the problem are, then it’s not normal.

Thanks for quick reply. Definitely not unbearable. Does it a few times at stoplight but not like it’s going to die or anything. It’s just so damn smooth everywhere else this stands out.

I’ll see if I can get anything meaningful in iPhone video.

[2017Z]

Thank you. It’s when it’s in drive. Neutral or park it’s smooth and I see the rom actually tick up to about 600 in N or P. 

 

So so on this fix, I’m not doing it, service is under warranty. Should I show them your suggestion or is there a GM advise I can refer them too. 

 

Thanks again. 

 

 

[20165.3Eco]

FYI, I just had the mounts done on my truck. I would say the rough idle is 90-95% gone. You can still feel an extremely slight shake every once in a while but I would have considered that normal operation not knowing any better.

 

Otherwise, the truck is much quieter and feels smoother at highway speed in v4 mode than before. Reminds me more of when it was newer and I first bought it now. 

[hirdlej]

1 hour ago, 20165.3Eco said:

FYI, I just had the mounts done on my truck. I would say the rough idle is 90-95% gone. You can still feel an extremely slight shake every once in a while but I would have considered that normal operation not knowing any better.

 

Otherwise, the truck is much quieter and feels smoother at highway speed in v4 mode than before. Reminds me more of when it was newer and I first bought it now. 

How long would you say they needed your truck in the shop to replace the mounts?  Is this something you can wait for or does it take more than a couple hours?

[MD11G200]

just to clarify you have the 5.3 right? I have a 6.2 and had it done and didn’t change a thing, idles so rough feels like it’s missing, had it done at 3K miles. They used the peko scope tool and the newer version mounts

[20165.3Eco]

You can't wait for it. This dealer has been notoriously awful and now that all of my warranty issues are taken care of I wont be going back. So they may be slower. Someone who has lots of experience should be able to get it done in a day no problem but not short enough to wait. 

 

Day 1: They didn't turn a wrench on the truck.

Day 2: Weren't finished

Day 3: It was finished around 4 pm. 

 

They had one or two other small things to do to the truck but nowhere near 3 days worth of work. Good thing they can stick Chevy with a rental car when they can't complete what they say they can.

 

Yes, mine is a 5.3. You can still feel a slight warble at idle sometimes and comparatively it is hardly noticeable to the original mounts. Hopefully these stand the test of time. If they didn't fix it it was going to be on the chopping block to trade out of GM. 

[Soulshine10]

Just bought a 2015 SLE 5.3 Liter with 39K miles on it. beautiful truck. I have a 12000 mile 1 year bumper to bumper warranty and have a reputable dealer.  AS soon as I drove it off the lot I noticed the vibration at idle. brought it back. The tech who drove it with me immediately agreed there was excessive vibration, The water bottle trick worked well. they cleaned the TB with no success and then researched and found TSB 17-NA-166.  Just brought it in today 4/12 to have the mounts changed out. hopefully this solves the issue. I'll follow up on this to report out what happened. Thanks for everybody's inputs as I was skeptical this was the issue. We'll find out I guess

[ic3man5]

This was my fix:

 

before:

 

After:

 

The truck runs at 212F usually fully warmed up so in gear its commanding 500RPM which is too low IMO. 660 made it go away.

[2017Z]

Sorry but what am I looking at?  Is this from a tuner and your readout?  How did you get this view?

 

ive thought about the tuner and ticking up idle

 

sorry not familiar with what you posted. 

[Soulshine10]

following up on my previous post. picked up truck sat 4/14 with new engine mounts and the vibration in gear at idle is just about gone. much better. Tech told me the R&R was much more involved Than what GM states. needless to say i'm happy with the repair. I do agree tuning the idle a bit higher will also improve the situation. I'm going to ask the dealer about it on Monday as I asked them to do this and it wasn't done. Wondering about the previous owner as he must have been able to tolerate the vibration??? 

On 4/12/2018 at 3:53 PM, Soulshine10 said:

Just bought a 2015 SLE 5.3 Liter with 39K miles on it. beautiful truck. I have a 12000 mile 1 year bumper to bumper warranty and have a reputable dealer.  AS soon as I drove it off the lot I noticed the vibration at idle. brought it back. The tech who drove it with me immediately agreed there was excessive vibration, The water bottle trick worked well. they cleaned the TB with no success and then researched and found TSB 17-NA-166.  Just brought it in today 4/12 to have the mounts changed out. hopefully this solves the issue. I'll follow up on this to report out what happened. Thanks for everybody's inputs as I was skeptical this was the issue. We'll find out I guess

 

[ic3man5]

On 4/14/2018 at 8:57 AM, 2017Z said:

Sorry but what am I looking at?  Is this from a tuner and your readout?  How did you get this view?

 

ive thought about the tuner and ticking up idle

 

sorry not familiar with what you posted. 

Its a screenshot from tuning software (HP Tuners to be specific). The row In Gear is the one you should look at the most, depending on engine coolant temperature the ECU changes the idle speeds.

[scale obsession]

I'm currently dealing with this on my truck. It's really bothering me. I've had it at two different dealers, and both say its within an acceptable range. It shakes my center console, to the point of being able to video it. It also shakes the seats, and is worse after a long highway run . I'm really frustrated. I feel like I've potentially made a large mistake on purchasing this truck. 

[2017Z]

I had the engine mounts replaced and it did nothing. 

 

My solution was a diablo intune. You can adjust the idle up 50 rpm at a time. It’s almost not noticeable now. Past the rough idle the tuner is freaking amazing. I thought I’d be returning it because did not believe the tuner could really do what everyone says it does with boost and gains. I was dead wrong. Truck is so much fun to drive. It has corrected all the complaints I had with lagging downshift or whimppy shifting. I’m a believer now. 

 

Ive done both the 91 diablo tune and their CAI jammer tune (I have a kn). Both are awesome and not sure which I like better. On both I adjusted the idle and the shift firmness and truck drives crazy good. 

 

I think the rough idle is mostly that it’s set to low for fuel standards and tuner can adjust. Interesting thing is, using the tuner actually got me better MPG!

 

best of luck 

[Jason Broswell]

I have had a 14 Sierra and a 16 Sierra and both have had idle issues. I installed a catch can on my 16 to stop the crankcase oil vapors from blowing back into the intake abs caking up the valves and throttle body. Odd thing in response to your post 

 

had my oil changed last week notified them of some odd squeak I had sounded like body flex or body mounts. They determined it was motor mounts. They had to order the parts and would replace under warranty. Today I picked up truck after they had it all day yesterday replacing the mounts and my rough idle is gone. 

 

So I would say they are correct in the rough idle being motor mount related. It had A rough idle when I took it in they changed mounts and. Now smooth idle it’s so nice too such a relief