2015 GMC Yukon Denali idle issue in 6.2 liter engine

[dvzzz]

I am in a somewhat similar position, was so excited to drive it home. Great condition GM company vehicle and CPO 2018 with 7000 miles. Mine misfires/misses, local independent mechanic told me yes he can easily feel it but no codes for it. Folks on these forums are sharing that is very common to rough idle like that but my 2 test drives I did show that they can idle butter smooth. Selling dealer told me - “no codes, nothing to fix, all 8- cylinder engines are like that, just live with it...” Why are you are you even thinking about trading it in for another GM? Chances are you can get a smooth idle with 2019 but feels like lottery, for me it is a lot of money to gamble with. I am seriously thinking about trading it in to older Nissan or Toyota 8-cylinder. I love how quiet my Yukon is, it has great looks. Almost everything I wanted except this idle.

So, the GM customer care in Canada was little help - not entirely her fault but funny how the story she was provided from the dealer was not true. She was told that they were logging the vehicle misfire count and codes - and I said, that would be great but hard for them to do when they don't have the truck in their shop. She was like what? I said, yes, me as a consumer / owner have installed my own data logger and will be doing my own case development. She tells me that's not right and I agreed but right now I have no choice. 
 
I'm still looking hard at trading it in for a 2019 but don't want to get into another can of worms.
 
Suggestions?

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[Bob2C]

Just take it in and tell the service advisor your truck has the symptoms outlined in TSB 17-NA-166. Make sure he notes that when you talk to him. If the dealership is good they will follow up. I did this with my dealer and they confirmed that was the issue. Took 3 days to fix because I have a cat back exhausted and the reading were off due to when they had to rev the engine. They explained in detail why it was taking longer but in the end new motor mounts and like I said earlier 95% corrected. I can live with that. But yeah it’s hit or miss when buying. I didn’t test drive mine because I bought it 600 miles away. Couldn’t pass up the deal. No one around me could come close in price.


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[dvzzz]

9 hours ago, Bob2C said:

Just take it in and tell the service advisor your truck has the symptoms outlined in TSB 17-NA-166. Make sure he notes that when you talk to him. If the dealership is good they will follow up. I did this with my dealer and they confirmed that was the issue. Took 3 days to fix because I have a cat back exhausted and the reading were off due to when they had to rev the engine. They explained in detail why it was taking longer but in the end new motor mounts and like I said earlier 95% corrected. I can live with that. But yeah it’s hit or miss when buying. I didn’t test drive mine because I bought it 600 miles away. Couldn’t pass up the deal. No one around me could come close in price.


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Thank you for this tip, I will try it again tomorrow with another dealer. I bought mine far away as well, it was the color/package/price that I needed to fit my budget. Rough idle really rears its ugly face only when fully warmed up and in D, did not sense it much in the cold test drive thinking fully under warranty with 7K miles and CPO. I have tried the M5 trick to ensure that AFM is not a factor and it does not change it in a slightest. I have tried Techron, and same - no change. Brand new engine air filter and again - no change. Either mounts or electrical. 

[Bob2C]

Thank you for this tip, I will try it again tomorrow with another dealer. I bought mine far away as well, it was the color/package/price that I needed to fit my budget. Rough idle really rears its ugly face only when fully warmed up and in D, did not sense it much in the cold test drive thinking fully under warranty with 7K miles and CPO. I have tried the M5 trick to ensure that AFM is not a factor and it does not change it in a slightest. I have tried Techron, and same - no change. Brand new engine air filter and again - no change. Either mounts or electrical. 

100% mount problem. I did exactly what you did. Good luck and keep us updated.

By the way get the range technology device to disable AFM. I have it and it drives much better.




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[ArrowsmithPML]

I still find it hard to believe it could be a mount but hey. As well, I bought it for the AFM and love that feature. I also bought it because it didn't need premium like all the other "premium / German" brands out there. Last year when premium fuel spiked in price to $2.05 per litre here on the west coast it was something I was so glad I didn't have to purchase.

[dvzzz]

I will keep everyone posted. Scheduled for tomorrow with another dealer.

100% mount problem. I did exactly what you did. Good luck and keep us updated.

By the way get the range technology device to disable AFM. I have it and it drives much better.




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[dvzzz]

My update from the dealer's visit. First of all I have provided them with all info that you helped me with here and then write up from the local ASE mechanic.

 

Advisor disagrees that mounts are the source of vibration, he felt that mount replacement will only mask the problem and I will be needing new mounts in 20,000 miles. In his mind this is a fuel injector problem but since there are no codes there is no way to find and nothing to repair until codes are showing. My question can injector be "misfiring" and no codes? What do I need to do to get them to repair? Can they say "it is operated as designed" as send us away and we have no recourse?

 

Regardless, they did not take the truck in saying I did not reserve the loaner, even though I had it in writing in the appointment confirmation email, but what are you going to do if they say they do not have  a loaner available? They are severely backlogged and it will several weeks before they have loaners avail. And this is the dealer with 4.5 rating, all other Chevy/GMC dealers are at 2.5 around here.  So far my experience with GM product and support was not stellar but I will call next week to see if we can schedule us in. 

 

[Bob2C]

When you say advisor do u mean the person accepting the vehicle or was it confirmed not to be the cause by a technician?


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[dvzzz]

37 minutes ago, Bob2C said:

When you say advisor do u mean the person accepting the vehicle or was it confirmed not to be the cause by a technician?


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I mean the person accepting the vehicle, he was reading my documentation. No, not confirmed by the technician. They did not even take the vehicle in. I got a feel that "no loaner" available is story is made up to make me go away to another dealer. 

[Bob2C]

Wow. That’s crazy. Yeah they tried that with me too. I was ok take me home I have a third car anyway. Keep it as long as you need as long as it comes back fixed.


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[dvzzz]

32 minutes ago, Bob2C said:

Wow. That’s crazy. Yeah they tried that with me too. I was ok take me home I have a third car anyway. Keep it as long as you need as long as it comes back fixed.


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I wish we could, we have been a Toyota single car household for the past 9 years, and never had to leave the car at the dealer not even once, I guess it never broke now that I am thinking. I did all maintenance on the Toyota so there was not even a need to take it to a dealer.

 

[Bob2C]

You mentioned the other dealer being a 2 star review. What about taking it to them. It’s worth a shot. I know I couldn’t take the rough idle much longer. Drove me crazy after spending all this money to have that.


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[dvzzz]

8 minutes ago, Bob2C said:

You mentioned the other dealer being a 2 star review. What about taking it to them. It’s worth a shot. I know I couldn’t take the rough idle much longer. Drove me crazy after spending all this money to have that.


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Yes, 100% I cannot take it either. Really drives me nuts but even more my wife who I convinced to buy an American truck. Such a fine interior and quiet ride but drives both my wife and I nuts to have these rough idle. I also noticed that it does not run smooth also when started cold in the morning ~1500-1700RPM, tach needle visible moves and it is misfiring even at the higher RPMs. 

 

These other dealers will be plan B next week. 

 

[Bob2C]

Yes, 100% I cannot take it either. Really drives me nuts but even more my wife who I convinced to buy an American truck. Such a fine interior and quiet ride but drives both my wife and I nuts to have these rough idle. I also noticed that it does not run smooth also when started cold in the morning ~1500-1700RPM, tach needle visible moves and it is misfiring even at the higher RPMs. 
 
These other dealers will be plan B next week. 
 

Here is my work order when I had my truck fixed. More ammo for you




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[dvzzz]

6 minutes ago, Bob2C said:

 

 

Here is my work order when I had my truck fixed. More ammo for you




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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.