Rough Idle = New Motor Mounts?

HondaHawkGT · February 24, 2017

I don't think I've seen a case of the warm idle vibe solved by new motor mounts yet. Maybe big powerful V8's are just too annoying for some guys.Tune the trueck to idle at 600 RPMlike 07Softail suggested if GM can't make your problem go away.

red262red6 · November 29, 2017

Just turned my 2017 Silverado 5.3l crew cab 153" wheel base in this morning and had it inspected for the vibration at idle when warm. I have watched it for many week and now that I am at 5,000 miles, no change. After about an hour they came back and said that after measuring the vibration it was found that mine is above the accepted range (good news that they are acknowledging it). So then I am informed that the motor mounts are possibly bad and that they are going to order new ones. I turn the truck in Monday to have them put in and will update if any change. But if not a tune is my next step as mine also goes away just above idle RPM, but not looking to void my warranty.

8lugCT · November 29, 2017

I feel like this is going to turn into an AFM issue

Sierra0919 · January 9, 2018

There is a bulletin PIP5211F (6/6/2017) concerning rough Idle and it states to replace motor mounts with new updated mounts. I ran into this replacing my own motor mounts for a different issue but figured this might help you guys. New PN for them are 84175580 RH/84175581 LH. I replaced mine with some aftermarket crap and found it made a big difference in the cab. You could definitely feel the engine through the cab and pedals.

If my truck was still under warranty I would definitely get them replaced.

Aftermarket crap I used were the Anchor 3275, It solved a rumble issue but will probably replace with updated OEM ones soon.

Obscenejesster · January 9, 2018

My rough idea has been fixed for the past month or so. I was running into the same scenario as you.

Get some Liquid Molly and follow the directions using a tank of premium fuel.

Fixed it for me.

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nluchau · January 10, 2018

On 1/9/2018 at 12:05 AM, Obscenejesster said:

My rough idea has been fixed for the past month or so. I was running into the same scenario as you.

Get some Liquid Molly and follow the directions using a tank of premium fuel.

Fixed it for me.

Sent from my LG-H932 using Tapatalk

Liqui Moly did nothing for me

20165.3Eco · January 10, 2018

Yeah, Liquid Moly didn't help one bit. If anything mine got worse. I've never actually seen a liquid additive fix a symptom although I do agree they are a necessary part of maintaining a clean fuel system.

Obscenejesster · January 10, 2018

Liqui Moly did nothing for me

Did you check your mass airflow sensor? That could have gotten dirty.

I honestly just think a lot of these idle problems stem from the factory idle being set roughly 50 to 100 RPM's too low. GM along with every other manufacturer are pushing these trucks to the limits in order to save fuel.

From the factory, the 495 RPM idle is fine but as soon as the motor gets broken in, loosens up or gets some mild carbon build up, the low RPM idle starts rearing its ugly head.

Those who get a custom tune and raise their idle RPM's by 50-100 always say that they no longer have a rough idle.

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20165.3Eco · January 11, 2018

Yep, no cast flashing on the housing and clean as a pin inside. Cleaned the TB as well and it had minimal buildup around the edges, probably didn't even need cleaned.Just a slight oil film in the intake, no excessive puddling like others have posted photos of.

I did notice today the idle was substantially better in the 55 degree weather we have. Been super cold lately, maybe the computer doesn't compensate properly for idle mixture with very dense air. 40,000 miles fyi. Haven't had enough warm days in a row to warranty any truth in this theory though.

Never noticed it in the summer, maybe cold temps and winter blend fuel exaggerate the issue. Does seem far less noticeable in reverse so I may try and get the goons to swap the motor mounts.

2017Z · January 29, 2018

My 2017 5.3 does the same rough idle. My kids call it the butt massage, thats how noticeable it is after the truck is driven. My Chevy Service rep said they are aware of the issue but the motor mount change does not work and also mine is not "rough enough" to get approved. Seriously? But even if it were he said the new mounts do nothing.

They did indicate that a engineer told them it is how the motor is set up for the emissions and fuel standards so basically noting will fix it other than increasing the idle with a tuner which then can "void" my warranty. GM wont address it because that would screw up their Govt submitted fuel standards for the truck and hello potential lawsuits.

Anyone have other luck with ticking up the idle to 650 range with a tuner?

GET1NE · January 31, 2018

I purchased a new 2017 Silverado last December and this issue has been a problem since the first week. It has been in the shop a grand total of 31 days over two service periods. The rough idle issue is one issue that I took it in for and they have replaced the engine and transmission mounts twice. This last time they upgraded the mounts and added shims as well. Just wanted to let everyone know the upgraded mounts did not resolve my issue. They now claim its within spec but the rough idle hasn't changed since the last service. I will be taking it back for a 3rd time tomorrow.

truckguy82 · February 1, 2018

Every k2 I’ve driven has a rough idle.

I guess it depends how rough you’re talking about. Its definitely normal to be rougher than most other cars you drive.

its get particularly worse with carbon buildup, and smooths out a bit after a crc intake spray clean. I do one before every oil change and notice the isle smooth out each time.

2017Z · February 1, 2018

I tried Seafoam spray and it did nothing. What’s the difference with CRC?

whi did you apply it on the Silverado. The seafoam was a PIA.

hirdlej · February 1, 2018

Has anyone bothered to do a cylinder balance test on one of these engines to see if there's possibly an injector that's not flowing the same as the others? This would be simple to do with HP Tuners. I'm going to be testing mine this spring. Perhaps something as simple as flow-matching the injectors would cure this.

truckguy82 · February 2, 2018

23 hours ago, 2017Z said:

I tried Seafoam spray and it did nothing. What’s the difference with CRC?

whi did you apply it on the Silverado. The seafoam was a PIA.

Seafoam/crc same thing as far as I know, i just buy it at walmart.

i spray it into the throttle body with the motor running at 2k rpm.

Just crack the intake hose off the throttle body, put a stick going from seat to throttle, move seat up, spray entire bottle into throttle for like 5 minutes. Shut off motor, give it a spritied drive 10 minutes later. Then I change the oil.

i notice the idle smooths out each time I do it