2015 GMC Yukon Denali idle issue in 6.2 liter engine

[Bob2C]

Really appreciate it! Thank you for all your help, I am glad I have your support.  With your help I will either fix it or will know that I cannot. 

Not a problem. This is what the forum is about. I have had plenty of people help me so now it’s my time to give back. I have learned soo much on this forum about the ins and outs of my truck. So glad I joined.


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[Bob2C]

One more thing. Don’t know if I sent this chart.




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[dvzzz]

6 minutes ago, Bob2C said:

One more thing. Don’t know if I sent this chart.




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Yes, I followed all of your posts and found it,  it was key to ensure that they even consider it for Yukon. Thank you. 

[ArrowsmithPML]

So, I spoke with the Service Manager of the purchasing dealership and I showed them the TSB and they pulled it up, reviewed it and said well looks like it might take a while to do the PICO test BUT that it is totally legit and if it addresses the roughness they are willing to give it a go. My issue is that I have an open case file with GM so I want to confirm that it won't make a mess of that process before I start something new. 

 

The interesting thing here is that the assistant SM has traded in her 2016 Yukon Denali for a 2019 of the same as hers was "idling so poorly" it was "going to fall apart" - now that coming from the inside of an office nearly floored me but it is what it is.

 

Based on deduction her issues were reduced by using premium fuel for about 6 months which I feel would have nothing to do with a motor mount but it got me thinking, is it possible that the higher octane burns at a different internal cylinder temperature and so if running regular would that somehow generate a vibration that is transferred to the mount location and shaking it loose? I don't know but seems plausible. 

 

They also stated that the AFM would have nothing to do with this but not seeing a cut away engineering drawing I'm not certain of that.

 

This just goes on and on... I feel we are getting closer to something though.

 

 

[dvzzz]

38 minutes ago, ArrowsmithPML said:

So, I spoke with the Service Manager of the purchasing dealership and I showed them the TSB and they pulled it up, reviewed it and said well looks like it might take a while to do the PICO test BUT that it is totally legit and if it addresses the roughness they are willing to give it a go. My issue is that I have an open case file with GM so I want to confirm that it won't make a mess of that process before I start something new. 

 

The interesting thing here is that the assistant SM has traded in her 2016 Yukon Denali for a 2019 of the same as hers was "idling so poorly" it was "going to fall apart" - now that coming from the inside of an office nearly floored me but it is what it is.

 

Based on deduction her issues were reduced by using premium fuel for about 6 months which I feel would have nothing to do with a motor mount but it got me thinking, is it possible that the higher octane burns at a different internal cylinder temperature and so if running regular would that somehow generate a vibration that is transferred to the mount location and shaking it loose? I don't know but seems plausible. 

 

They also stated that the AFM would have nothing to do with this but not seeing a cut away engineering drawing I'm not certain of that.

 

This just goes on and on... I feel we are getting closer to something though.

 

 

What was concerning that advisor sounded like they had seen it few times with injectors being at fault. However, it felt like this is the work that they are not interested in. He did not say that but it was obvious that he was willing to risk a scandal (I had to take time off work to drop off the car and I had loaner reserved and confirmed.) We came to live in times where dealer does not have to worry about customer care, and if dealer and GM do not want to work on it they can send us packing. My theory on that is - GM does know about this narrow manufacturing defect or has difficulty balancing 8-cylinder as it would reduce the manufacturing yield, it is much cheaper to adjust computers to ignore this misfiring and recording a code. I know it is a conspiracy theory but at the end of the day in the age of profit-driven decision-making customer care is not a factor and does not matter. Again, yes conspiracy theory that is not likely to be confirmed ever. 

 

Edited October 4, 2019 by dvzzz

[dvzzz]

Another update. Apparently Chevrolet or GMC dealers in the area all except one do not offer loaners, only ride homes within 10 miles. The dealer with a loaner program that I have tried last week did not give me the scheduled loaner. Wanted to ask this forum. Is it common for Chevy or GMC dealers not to offer loaners to warranty customers? All of my Toyota dealers in my experience do offer you a vehicle if work is more than 2 hours. My understanding that GM does not provide vehicles for warranty repairs and it is at dealers' good will to offer one? I will be renting a car to get the vehicle diagnosed on Thu, until it is diagnosed, I do not have a case anyway.

I did more digging and it looks when mounts are at fault with increase in RPMs even a minor 50-100 RPMs idle flutter disappears, it is not also present in P or N. On my truck I feel it in D, P, N or even when I press on accelerator to increase by 50-100 RPMs, I still feel the skipped beat even at 1200 RPMs. 

OBD also shows that when motor "skips" at a stop in D RPMs fluctuate between 480 and 520 briefly, when no skips motor stays at around 500-505.

[Bob2C]

Loaners are a courtesy and not required for warranty work by GM. Dealer discretion. What I have noticed if you bought the car there they are more likely to give you a loaner. I would just keep pressing the dealers to get your issue resolved. Spend all this money and have an annoying idle problem. I know how that feels.

 

My idle RPM is the same as your situation. Mount replacement cleared 95% of it up. The idle fluctuation is there it’s just not noticeable. I too have used the scanner to read RPMs

 

 

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[dvzzz]

8 hours ago, Bob2C said:

As expected after 4 hours dealer called me back saying "no problem found, they are all like that. You have to live with it. We do not see codes or sense anything abnormal. Sorry we cannot fix what is not broken... "

Now how do I prove that is broken? I am learning dealers are instructed to use "work as designed" for non obvious or critical defects, as it reduces warranty costs, is there a way to get an independent opinion that they must respect? I brough a paper from the independent  ASE mechanic but that did not seem to have any bearing on them...

 

 

Loaners are a courtesy and not required for warranty work by GM. Dealer discretion. What I have noticed if you bought the car there they are more likely to give you a loaner. I would just keep pressing the dealers to get your issue resolved. Spend all this money and have an annoying idle problem. I know how that feels.

 

My idle RPM is the same as your situation. Mount replacement cleared 95% of it up. The idle fluctuation is there it’s just not noticeable. I too have used the scanner to read RPMs

 

 

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[Bob2C]

That just terrible. I guess I was lucky with my dealer. I have like 5 within a small radius so I guess that might help. I really don’t know what else you can do other then call the gm number and open a case and be specific. Just keep raising hell. Squeaky wheel gets oiled.


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[dvzzz]

2 hours ago, Bob2C said:

Yes, this is getting interesting, they are testing my patience. Quick read shows that cost of warranty is very significant to car makers these days and they instruct dealers to keep those in check, thus they do not want to deal with non-critical issues. GM is not my friend in this case but I still will open the case of course. When a police vehicle with 17K miles runs smooth and 7 months old 8K miles truck does not... I only need to find a way to document it. 

 I went to pick up the vehicle and they gave me 2018 Tahoe police vehicle to feel. Zero flutter on that one. Techs came out sat in mine and said, they do not feel anything either. Gave me the scope results showing <2 g (actually 1.26g) results on it, saying that I am within GM's range. I asked, how did you measure, etc. they said, we know how to do it. Conundrum. I drove away and at a first light it fluttered. OBD show fluctuations when it happens this video shows from 480 to 510 in D at a full stop engine at 210F  https://youtu.be/jl9q3M87FLo

 

 

2 hours ago, Bob2C said:

That just terrible. I guess I was lucky with my dealer. I have like 5 within a small radius so I guess that might help. I really don’t know what else you can do other then call the gm number and open a case and be specific. Just keep raising hell. Squeaky wheel gets oiled.


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[Bob2C]

This was also another solution someone did to bump idle up 50 RPM. You see when at 212 the computer sets idle low. Obviously when cold it’s higher

 

Some did a diablo tune to adjust as well

 

 

Rough Idle = New Motor Mounts?

https://r.tapatalk.com/shareLink/topic?share_fid=33003&share_tid=195971&share_pid=2104873&url=https://www.gm-trucks.com/forums/index.php?/topic/195971-Rough-Idle-%3D-New-Motor-Mounts%3F/page__view__findpost__p__2104873&share_type=t&link_source=app

 

 

 

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[dvzzz]

Another dealer gave me an answer saying "all within GM's ranges for vibration" no issues detected anywhere. Problem is that GM sets these thresholds to whatever and nobody other than GM really controls what acceptable and what is not. This is not unique to GM, entire industry now found the loophole of "within spec" and abusing it. An only exception I have seen was Lexus. They work on the problem until you are happy, I had two of their trucks and they worked on one for 1 week until they found the problem. Hyundai  says that 100s of shaking Palisades and Tellurides at 65 miles per hour is "within spec". Unless it is a safety hazard regulators would not get involved. This starts to feel fishy to me that $65K vehicle idles like Russian Lada from 1980... but it is "by design". Independent mechanics document that they see the problems but vehicles are in warranty. In my case mechanic saw the problem and wrote it up. 

 

We losing consumer power every day... Hate to feel so powerless, I guess I have to dump this byproduct of the joint GM/Lada venture... 

Edited October 11, 2019 by dvzzz

[Bob2C]

Just unbelievable. If you dump it your going to take a hit on depreciation. Drive it hard for a year or two maybe and then get rid of it


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[dvzzz]

1 hour ago, Bob2C said:

Just unbelievable. If you dump it your going to take a hit on depreciation. Drive it hard for a year or two maybe and then get rid of it


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I agree too much of a loss, but I have developed such a rejection of General Motors product that I have to either learn to live with it every day hating GM and GMC logo or just go back to the trusted Japanese trucks. Why did I believe that American cars are now able to compete with Japanese is beyond rational, I guess I liked the look of Yukon and perhaps was listening to Bruce Springsteen when I was making that buying decision but as parents have been teaching looks is not everything  Need to find some humor in this lemon of a situation. 

[Bob2C]

The one thing American cars always had over the foreign cars was ride comfort. I always found the American cars to have a soft ride. I just came back to GM after 10 year break. As I use my truck I find quality issues. They need to step up their game if they really want to compete.


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