Rough Idle = New Motor Mounts?

[hirdlej]

I still contend it has to do with an unbalance of the firing of the engine.  Not the firing order but at a low speed there's cylinder pressure being bled off, weak spark or an imbalance of fuel making its way into all 8 cyls.  Is it fuel?  Valves not seating? Rings?  something related to AFM? The lower the engine speed, the more sensitive an engine is to any flaws in operation.  The first test would be a leakdown and compression test of all 8 cyls.  If those were good I would flowmatch the injectors.  If that's all fine then I'd be looking at spark.  Maybe it has something even to do with the cam lobes on 4 of the cyls being different than the other 4 (AFM camshafts aren't symmetrical)

[Justin101714]

Don’t know what the issue is with you’d guy’s trucks, but every single one I’ve ever had a complaint about a consistent rough idle while in drive, the engine mounts fixed every one of them.


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[2017Z]

Maybe we can compare the part # off your service form to mine and make sure they are the same. 

 

I had hoped this would have worked but no go. 

[hirdlej]

Still waiting for those part numbers on the updated mounts.......

[Justin101714]

Okay, part number according to the bulletin #17-NA-166

V6 Pick up RH - 84175578
V6 PU LH - 84175579
V8 PU RH - 84175580
V8 PU LH - 84175581
V8 SUV RH - 84175582
V8 SUV LH - 84175583


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[MD11G200]

On 3/2/2018 at 3:55 PM, Justin101714 said:

Don’t know what the issue is with you’d guy’s trucks, but every single one I’ve ever had a complaint about a consistent rough idle while in drive, the engine mounts fixed every one of them.


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Do you work for GM? You said “every single one you had Complaint about”

 

[Justin101714]

Yes, I work for several dealerships throughout the south east.


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[15 Z71]

3 hours ago, Justin101714 said:

Yes, I work for several dealerships throughout the south east.


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My 15 Sierra has a rough idle but not all the time. It only does it once in awhile when I'm at a stoplight or stop sign. If it where the mounts wouldn't it do it all the time?

[Justin101714]

No, they are hydraulic mounts. If it doesn’t do it quite consistently, leave it alone. In 2007-2014 older body style trucks, there was a bulletin that stated a slight stumble when at a stop in drive is normal operating for the V8 platforms. I’ve noticed this “stumble” on numerous body styles since the early 2000’s.


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[15 Z71]

1 hour ago, Justin101714 said:

No, they are hydraulic mounts. If it doesn’t do it quite consistently, leave it alone. In 2007-2014 older body style trucks, there was a bulletin that stated a slight stumble when at a stop in drive is normal operating for the V8 platforms. I’ve noticed this “stumble” on numerous body styles since the early 2000’s.


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Ok thanks. It just seems like you can feel it in the seat and if you just give it a little throttle it goes away. I guess I will just leave it then unless it get real bad. 

[DONWT15]

2 hours ago, Justin101714 said:

they are hydraulic mounts

Are you saying they collapse?

 

"They are getting internally grounded inside the mount" from your post earlier in this thread

 

Sounds like they collapse and cause hard contact with the frame.

 

 

So in conclusion if your engine runs rough, mount it in a bowl of jello and so you won't feel it any more.

Edited March 13, 2018 by DONWT15

[Justin101714]

Even the old mounts are fluid filled as well. These mounts have been used for years over several different car lines. But yes, they ground out internally, and the vibration is felt through the frame.


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[silveradosid]

justin i dont have the rough idle problem but when it switches to v4 mode the truck vibrates really bad , i dont have any codes or vibrations except v4 mode would these new mounts fix this problem. it is a 2014 5.3 ccsb 4x4 

[MD11G200]

On 3/12/2018 at 3:08 PM, Justin101714 said:

Yes, I work for several dealerships throughout the south east.


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OK no offense but since you work for  GM I will disregard anything you say.

 

[Justin101714]

OK no offense but since you work for  GM I will disregard anything you say.
 

Doesn’t hurt my feelings one bit man. You’ll just continue to have broken shit. I’ve contributed in favor to a lot of forum members on their problems with their trucks and SUV’s. Is everyone going to agree, no.....but that’s okay. We’ll just keep things moving and you’ll get left behind. Do everyone a favor though, go trade your truck in and get something else from a different manufacturer so we don’t have to see your pissing and moaning. Trust me, the loss would be beneficial to GM. They’ll just sell it to someone else who’ll like the truck and organization behind the truck.


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