Rough Idle = New Motor Mounts?

SavageSierra · January 5, 2017

I took my 2015 GMC Sierra 4x4 in for a rough idle that i have been having which is most noticeable when the vehicle is up to operating temp and in gear at a stop. The dealer shimmed the motor mounts but was unable to get the rough idle to go away. They said they called "GM" and they told them to replace both motor mounts because they are apparently defective. Has anyone ever experienced this and was it successful?

diyer2 · January 5, 2017

Sounds dumb to me.

SavageSierra · January 5, 2017

anyone else?

GMCustomerService · January 5, 2017

Hello SavageSierra,

We apologize for the unexpected rough idle concern with your Sierra. If you would like for us to look into this further, and reach out to the dealership, let us know in a private message! Be sure to include your VIN, current mileage, contact information and servicing dealership.

Kindly,

Anthony

GM Customer Care

BIGDOGx · January 6, 2017

I know a tech at my dealership stated that the terrible tunes these trucks have are the fault of weak motor mounts and them not being able to handle the torque of these engines. He said they were snapping them off the frame, not sure how much truth their is to it but would make a lot of sense considering how easy it would be for gm to tune these trucks correctly and them refusing to do it.

hunthearin · January 8, 2017

Same issues with my 2016 5.3 Sierra. I've read in one post that the rough idle is due to buildup on the fuel injectors. Another post says it is due to the low idle RPM, and that it can be fixed with a tune. Either seem likely to me - mine happens right at 500 RPM.

Who knows what the dealer will tell me. Probably that it is "within GM spec" or that they "can't duplicate the problem." Of course, they'll tell me that at 5:50 PM, after keeping truck all day.

nluchau · January 9, 2017

How rough is "rough"? After mine gets up to operating temp the RPM's lower to about 400ish and I can definitely feel the motor running. Anything higher RPM and I cannot feel it. It's not very rough though, just enough for me to feel it running. 2016 Silverado 5.3 - 6 speed.

SavageSierra · January 10, 2017

Mine is only noticeable at idle when warm. I've had the truck since new and right off the lot you could feel the engine running but it was still smoother than it is now. Passengers that aren't familiar with the truck notice it and it will make water inside of a bottle move quite a bit. The thing that shocked me is that the dealer actually acknowledged the vibration issue, which is cool I guess.

07Softail · January 10, 2017

I idled mine up to 600 and you wouldn't believe how much smoother it idles now.

RT

nluchau · January 10, 2017

I idled mine up to 600 and you wouldn't believe how much smoother it idles now.

RT

Mine idles great when it's not up to operating temp aka 600rpm.

HondaHawkGT · January 10, 2017

New bulletin for rough idle concern:

http://sandyblogs.com/techlink/?p=6999

DannySierra · January 18, 2017

2016 regular cab sierra 5.3 same problem, took it in, and same, shims on the motor mounts. I think its worse now, and yeah only at idle when warm. All your problems i have as well. Let me know if it gets fixed with new mounts

HondaHawkGT · January 19, 2017

There's a new potential cause of for a rough rough idle.

http://sandyblogs.com/techlink/?p=6999

Harsh Shift and Rough Idle Conditions

October 9, 2016

A harsh shift and rough idle may be felt on some 2014-2017 Corvette, Silverado, Sierra; 2015-2017 Escalade, Suburban, Tahoe, Yukon; 2016-2017 CTS-V, and Camaro models.

The harsh shift may be felt on the 1/2 and 2/3 shift along with a sputter when applying the throttle between 0% and 30 % and a rough idle. DTCs P0101 (MAF Sensor Performance), P0171 (Fuel Trim System Lean Bank 1), P0172 (Fuel Trim System Rich Bank 1), P0174 (Fuel Trim System Lean Bank 2) and P0175 (Fuel Trim System Rich Bank 2) may be set.

Inspect for cast flashing in the air filter housing near the Mass Air Flow (MAF) sensor for excessive flashing. (Fig. 11) If excessive flashing is found, replace the air filter housing lid. Be sure to check the flashing in the new lid as well.

HondaHawkGT · January 21, 2017

Same issues with my 2016 5.3 Sierra. I've read in one post that the rough idle is due to buildup on the fuel injectors. Another post says it is due to the low idle RPM, and that it can be fixed with a tune. Either seem likely to me - mine happens right at 500 RPM.

Who knows what the dealer will tell me. Probably that it is "within GM spec" or that they "can't duplicate the problem." Of course, they'll tell me that at 5:50 PM, after keeping truck all day.

Every single brand will tell you it's either normal or cannot duplicate. From Honda to Toyota to Ford to GM, rough idle will go unfixed 99.9999% of the time. Too many possible causes (some being unfortunate side effects of the race to better fuel economy and emissions) to know what's causing every vehicle's rough idle. Fuel quality, fuel injectors, engine mounts, emissions system, torque converter, vacuum leaks, MAF sensor problems, ignition system, etc etc etc.

SavageSierra · February 24, 2017

2016 regular cab sierra 5.3 same problem, took it in, and same, shims on the motor mounts. I think its worse now, and yeah only at idle when warm. All your problems i have as well. Let me know if it gets fixed with new mounts

Had the new mounts put in didn't solve the issue.