Anyone else had issues with faulty motor mounts causing a shake/vibration at idle

Rcfire · October 15, 2021

So been battling this rough idle vibration at idle. Stop lights etc everything on the truck checks out but found a service bulletin stating faulty motor mounts could be causing the sensation of a rough idle or misfire. Been in the Chevy dealership in Lubbock to twice and they keep saying everything is fine. The service tech told me there is no service bulletin or anything regarding this issue. Upon further research on this I found a service bulletin stating my exact issue. I brought it to the dealerships attention and they played dumb like they didn’t know. So frustrating. Taking it to another dealership Monday. Has anyone else had this issue and did shimming or replacing the motor mounts fix it ??

2021 Silverado 6.2. 4000.00 miles

Edited October 15, 2021 by Rcfire

Jonathan Ortiz · November 17, 2021

Hi RC I have a 21 5.3 sierra with 12,000 mi and I’ve noticed multiple times when I come to a light I feel a slight rumble under my seat and a little rattle behind the center dashboard. I explained to the service advisor on my last service what was going on but i was told no light no issue so far I’m the only person who feels the shake and until coming across your post I thought I was crazy. Do you happen to know what service bulletin I need to look up so I have some proof of my issue?

Rcfire · November 18, 2021

23 hours ago, Jonathan Ortiz said:

Hi RC I have a 21 5.3 sierra with 12,000 mi and I’ve noticed multiple times when I come to a light I feel a slight rumble under my seat and a little rattle behind the center dashboard. I explained to the service advisor on my last service what was going on but i was told no light no issue so far I’m the only person who feels the shake and until coming across your post I thought I was crazy. Do you happen to know what service bulletin I need to look up so I have some proof of my issue?

There is a service bulletin out but not sure where I found it. The dealership can look it up by your VIN. I have had my truck in the shop three times and they say it’s normal. It is driving me crazy and I am about to just be done with Chevy. A brand new 2021 truck should idle smooth. It’s so annoying. I really think it’s the motor mounts but they won’t replace them

voided3 · November 19, 2021

The rough idle seems to, unfortunately, be an intrinsic characteristic on the 5.3 and 6.2 engines. Our '21 Silverado with the 5.3 with a little over 11,000 miles on it also dances around a bit at 500 RPM, mostly on a cold start after warming up for 20 seconds or so and not so much when up to temperature. I have done cold starts with the hood open so I could watch the engine move and there does seem to be a good amount of engine shaking happening side to side, but I'm guessing they are heavily dampened rubber mounts for noise isolation which allow that much play.

Some have reported that running higher octane gas can smooth idle, but I always run our 5.3 on at least 89 octane (extra knock protection for towing) and it still does it. Some also reported that having auto start/stop engaged seems to reduce this (when the engine is actually idling with it engaged, obviously not when it's off at a stop light haha), but I always turn it off reflexively every time I drive the truck.

I would honestly do your best to ignore it and just keep up with maintenance. After nearly a year of ownership, I've learned to live with several annoyances that seem to be characteristics of these trucks, the biggest being DFM (which I disable by driving in L7 on the 8-speed), but the various squeaks/rattles/clunks/vibrations I routinely experience all seem to be normal for now. Let's just say if I didn't need a truck, I wouldn't be putting up with it.

customboss · November 30, 2021

"told no light no issue"

In work as a expert witness and forensic oil analysis for 42 years warning, EVERY OEM is having issues with quality of coils. The coils are very difficult to test unless the technician is a electronics tech with appropriate gear like a O scope.

Diagnostics onboard the GM trucks are designed to alert or lite MIL codes for emissions issues out the tailpipe or leak of fuel vent systems. NOT ACTUAL ENGINE PERFORMANCE.

Dealer diagnostics can detect a lot but not necessarily partially failed coils or contacts to boots and plugs and coils. Corrosion can show similar issues.

Engine oil analysis that shows gas chromatographic fuels dilution of engine oil and FTIR nitration can identify issues like these without advanced electronics testing.

DO NOT accept poor service when the design is not bad. You have options as a customer.

M1ck3y · December 5, 2021

These engine's have always been a little rough. Gm does tune them right up to, and on the edge of a misfire for emissions purposes. Custom tune will usually raise the rpm to 650, which smooths it out.

Its also the nature of direct injection, large ports = slow velocity (low in the rpm) = poor atomization