Rough idle when coming to stop

Rosedog · August 16, 2016

So my truck went in today for the idle re-adjustment...just got the call that with the frequency that they were getting that Chevy is sending out new redesigned motor mounts. Take that as you will.

Dnt · August 17, 2016

Now the dealer says its my ahead and its now with in specs, dropped my son off at karate last night went into the store and came out and the truck would not start. It took a little while, calling on star, my wife to pick up my son but finally figured out they have linkage in shift lever messed will not go into park according to the instrument panel. It started in neutral and has an issue with going into park so its back to the dealer so tired of this.

That is the reason that I hate to take my truck to the dealership there always seems to be a return visit to try to fix something else that they messed up. The attached video is from before I had the dealership monkeys install the GM Borla exhaust last week. I have not recorded a after exh video but i can still feel the engine shake at idle so know it is still there. I do not see how this could be a motor mount issue? It looks like the engine is simply running rough? The entire engine seems to shake every few seconds...... I use Shell 93 octane fuel and have around 3200 miles on the truck it is a 2016 CC SB 6.2 8spd 3.42 gears

https://www.youtube.com/watch?v=GbWw5VSntOM

huntr1117 · August 17, 2016

My 2017 6.2 has the same shake at idle. It's pretty noticeable when sitting at a red light. Even my passengers ask if the truck has a miss. The rpms drop every time it shakes. I haven't brought the truck in yet though.

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tylerrmack · August 17, 2016

That is the reason that I hate to take my truck to the dealership there always seems to be a return visit to try to fix something else that they messed up. The attached video is from before I had the dealership monkeys install the GM Borla exhaust last week. I have not recorded a after exh video but i can still feel the engine shake at idle so know it is still there. I do not see how this could be a motor mount issue? It looks like the engine is simply running rough? The entire engine seems to shake every few seconds...... I use Shell 93 octane fuel and have around 3200 miles on the truck it is a 2016 CC SB 6.2 8spd 3.42 gears

https://www.youtube.com/watch?v=GbWw5VSntOM

This is exactly what my truck is doing! Same engine/setup. I cant stand it. Did the exhaust help at all or would a new video reveal the same shake? If you find any fixes PLEASE post! Still thinking independent shop but havent had time. Either that or FORD.

tylerrmack · August 17, 2016

That is the reason that I hate to take my truck to the dealership there always seems to be a return visit to try to fix something else that they messed up. The attached video is from before I had the dealership monkeys install the GM Borla exhaust last week. I have not recorded a after exh video but i can still feel the engine shake at idle so know it is still there. I do not see how this could be a motor mount issue? It looks like the engine is simply running rough? The entire engine seems to shake every few seconds...... I use Shell 93 octane fuel and have around 3200 miles on the truck it is a 2016 CC SB 6.2 8spd 3.42 gears

https://www.youtube.com/watch?v=GbWw5VSntOM

Another thing. You should try revving up the engine (i used a golf club on the gas to keep a constant rpm better) and check the engine. Mine still shakes even at 1500 rpm and above. Which makes me think its doing it constantly and throughout driving but its harder to tell with road vibrations. Which leads to annoying paranoia when driving!

I had a #2 misfire/failed spark plug fixed. Thought maybe it was oil from pcv. But put a catch can oil as a expirement. Turns out it works well. Oil pooled behind throttle body, then cleaned out and got oil in again within 100 miles. Then catch can installed. No oil for 500 miles. Took it off for expirement and oil back at 300 mile check. Didnt help vibration. Didnt try CRC cleaner yet. Thats next step before reinstalling catch can.

Dnt · August 17, 2016

This is exactly what my truck is doing! Same engine/setup. I cant stand it. Did the exhaust help at all or would a new video reveal the same shake? If you find any fixes PLEASE post! Still thinking independent shop but havent had time. Either that or FORD.

Yes it is the same the exhaust had no affect on the shake but it sure sounds good now LOL. I am going to run outside and hook my OBDII reader up and see if any codes on it I guess. It is intriguing that someone has already had a spark plug fouling issue. Will report back if the code reader pops up anything. Check out this Borla exhaust though man, Expensive as heck but worth every penny IMHO

OK I did not have any stored codes but had a yellow light on the Innova 3160 code reader and a pending code U0073 (control module communication Bus Off) Anyone else seen that? My truck has 3360 miles on it! Only thing I have noticed is this shake at idle could this code U0073 cause that? Might just be normal?

tylerrmack · August 18, 2016

I hope its not normal and can be fixed. Not something ai would expect out of such an expensive modern vehicle. If it was designed this way then I have no respect for GM engineers. At least exhaust can be remove from equation. Did they remove all the way to the exhaust manifold thus eliminating any leaks there? The only code I have ever gotten was p0300 for my fouled plug/misfire issue. I do notice the low side fuel pressure fluctuating at about the same frequency. Idle mid 40s psi with periodic dips into low 30s and 20s

Dnt · August 18, 2016

New exhaust is a GM Borla cat back system dealer installed. The truck has 3 cats 1 on each exhaust manifold that Y into one large Cat. The GM Borla exhaust ties onto the outlet of the third cat replacing the factory system (CatBack) I did notice a fluctuation of the fuel pressure and the idle speed was up and down too. If it actually sets a code I will take it back to the dealership not sure they will do anything about a pending code? Might check it again this weekend to see if I can jot down some readings to compare to others. Note the pending U0073 code was in the ABS area of the Innova 3160 reader.

tylerrmack · August 18, 2016

New exhaust is a GM Borla cat back system dealer installed. The truck has 3 cats 1 on each exhaust manifold that Y into one large Cat. The GM Borla exhaust ties onto the outlet of the third cat replacing the factory system (CatBack) I did notice a fluctuation of the fuel pressure and the idle speed was up and down too. If it actually sets a code I will take it back to the dealership not sure they will do anything about a pending code? Might check it again this weekend to see if I can jot down some readings to compare to others. Note the pending U0073 code was in the ABS area of the Innova 3160 reader.

Whats you build date? And does this shake look familiar to anyone else on here with a 6.2l?

dbt1127 · August 18, 2016

So my truck went in today for the idle re-adjustment...just got the call that with the frequency that they were getting that Chevy is sending out new redesigned motor mounts. Take that as you will.

Can you tell me what the idle readjustment is. I have asked my dealer about this because I feel like my idle is to low, but they said that they can't touch the idle.

Rosedog · August 19, 2016

Can you tell me what the idle readjustment is. I have asked my dealer about this because I feel like my idle is to low, but they said that they can't touch the idle.

Good question! Short answer is I don't know. When I took it in to get it done, they called me back and told me with the frequencies they were getting that Chevy was sending them new redesigned motor mounts to install. Just waiting for them to arrive now.

Dnt · August 20, 2016

Whats you build date? And does this shake look familiar to anyone else on here with a 6.2l?

Build date January 6 2016 so "Wednesday" build SUPPOSED to be a better chance of having a good one if mid week build LOL

tylerrmack · August 20, 2016

Build date January 6 2016 so "Wednesday" build SUPPOSED to be a better chance of having a good one if mid week build LOL

Mine was 11/15. I wonder if GM has made any changes to components since January? I have heard they quietly switch or update parts in factory that they figured I out are problems. Another symptom I forgot to mention was when very slightly easing off brake, just enough to barely move foward like in slow traffic, my truck surges/bucks. This is more prevelent when cold. Have you noticed this? Or noticed the vibe even at higher rpm in park?

HondaHawkGT · August 21, 2016

Mine was 11/15. I wonder if GM has made any changes to components since January? I have heard they quietly switch or update parts in factory that they figured I out are problems. Another symptom I forgot to mention was when very slightly easing off brake, just enough to barely move foward like in slow traffic, my truck surges/bucks. This is more prevelent when cold. Have you noticed this? Or noticed the vibe even at higher rpm in park?

The vibe changes when you let off the brakes, or when it's cold, or when you put it in park because of the torque converter. Which supports the idea that your vibration issue is rooted on the torque converter, not motor mounts like some guys believe.

tylerrmack · August 21, 2016

The vibe changes when you let off the brakes, or when it's cold, or when you put it in park because of the torque converter. Which supports the idea that your vibration issue is rooted on the torque converter, not motor mounts like some guys believe.

The torque converter would cause these intermittent vibrations like a misfire every few seconds (video)? Even in park, nuetral? I thought thr tranny was uncoupled in park and nuetral?