2015 GMC Yukon Denali idle issue in 6.2 liter engine

dvzzz · October 23, 2019

I agree with you quiet cabin of Yukon is nice, but the fact that neither dealer nor GM are interested in fixing my issue and that three different mechanics agree unstable idle exists but they do not know why is very surprising for $60K car. I found a local GM expert performance shop. These guys are known for their integrity among Corvette enthusiasts. They will charge me $200-$400 to diagnose and if they find the problem I am not convinced that their finding would not fall into "within spec" trap. I am willing to spend this money and if GM/dealer still sends me to pack sand, I am the least litigious person in the world will go to Attorney General of the State. My wife is rightfully mad now as she drives it every day and hates the idle feel, truck also started to surge/jump when it comes to a stop or when goes from coasting on almost idle to acceleration.

Edited October 23, 2019 by dvzzz

ArrowsmithPML · October 23, 2019

An update on my case, a new service dealer has agreed to take on the challenge and using their recommendations of using premium fuel for a while - which is just about $2.00 per litre I might add! has reduced the issue but has not solved it. This dealer has begun the TSB for the engine mount but wit the strike the parts are delayed and may also get stuck at the boarder for a short period of time. I'm fine with that as at least I am moving forward.

dvzzz · October 24, 2019

How did you get the dealer to consider the mount replacement? In my case they are saying picoscope is 1.5G on mine which is less than GM's acceptable 2G. I am reading that picoscope measurement setup is so touchy that tech can make any measurement <2G. Truth remains that my Yukon irregularly hesitates in D and now even in P (in P a bit less noticeble). I have tried the Premium fuel but Hendrick GMC in Durham NC has told me not to put Premium in 5.3, period do not put premium in it, it burns differently, that is what Master Tech told me...

On 10/23/2019 at 9:34 PM, ArrowsmithPML said:

An update on my case, a new service dealer has agreed to take on the challenge and using their recommendations of using premium fuel for a while - which is just about $2.00 per litre I might add! has reduced the issue but has not solved it. This dealer has begun the TSB for the engine mount but wit the strike the parts are delayed and may also get stuck at the boarder for a short period of time. I'm fine with that as at least I am moving forward.

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Edited October 28, 2019 by dvzzz

dvzzz · October 29, 2019

Interesting theory emerged from one experienced GM mechanic who is also a GM big truck fanatic, he sees similar issue and repaired it by replacing ATF transmission issue, first run it with anti-shudder additive and then replace with fresh ATF and filter. I am not sure how exactly that might help with rough idle but he feels that it is most likely. Open to thoughts and ideas on this suggestion. My truck is only 8,000 miles at the moment.

ArrowsmithPML · December 6, 2019

Well guys,

I took this TSB referenced in this note to the local dealer. Explained the issue and had the first part of the test run and proven with the PICO meter and after waiting a number or weeks for the parts, due to the strike and issues at the boarder, I finally had the work done yesterday and so far, I can positively say that I do not have any vibration or shudder (so far, fingers crossed). This is what a Denali should drive like - smooth as silk.

Obviously, a little early to be 100% certain but I feel we are pointing at if not over the finish line here.

Cheers,

dvzzz · December 6, 2019

21 minutes ago, ArrowsmithPML said:

Excellent to hear that.

I was asking my dealer to do engine mounts replacement on my Yukon but they said GM instructs not to do mount replacements any more as this is only a temp fix. Please keep us posted on how things are as you drive it more. If your fix is permanent, I will chase the dealer on my side to do it.

Well guys,

I took this TSB referenced in this note to the local dealer. Explained the issue and had the first part of the test run and proven with the PICO meter and after waiting a number or weeks for the parts, due to the strike and issues at the boarder, I finally had the work done yesterday and so far, I can positively say that I do not have any vibration or shudder (so far, fingers crossed). This is what a Denali should drive like - smooth as silk.

Obviously, a little early to be 100% certain but I feel we are pointing at if not over the finish line here.

Cheers,

ArrowsmithPML · December 7, 2019

I find that a TSB that was just released in September more of a permanent fix vs something that someone might consider temporary. Frankly, I think that is a lazy answer and I would seek the advice of another place. I went to the other dealer and sat with the service manager in his office for about 90 minutes and we talked about everything, good, bad and indifferent. You won't get anywhere by being an ass so I always go in real nice and see where that leads.

Thanks

dvzzz · December 7, 2019

Indeed. Great to hear that. I found a really friendly dealer, Service Manager is willing to help but telling me that GM does not allow them to do mounts because picosope gives vibration measurment at 1.5 which is <2. GM authorizes mount only if picoscope shows 2++. Do you happen to know what were your measurements on the picscope?

Bob2C · December 7, 2019

Here’s what mine said

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TXGREEK · December 7, 2019

Here’s what mine said

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Way to go, Decline! Decline! that worthless wash!

Sent from Above

TXGREEK · December 7, 2019

I’m going to get mine checked out too [emoji6]

Sent from Above

dvzzz · December 7, 2019

Looks like they did check for this TSB too

ArrowsmithPML · December 7, 2019

Mine was recorded as similar. #17-NA-166 and pico scope analysis done with spikes to 4.8, then 2.8 and then 1.8 at times - very erratic and unpredictable.

Anyone that has this vibration issue should really do everything they can to address is.

I was advised to run a few tanks of premium fuel - which I did and noticed a slight correction but it never went away. We had 3 of the 8 injectors replaced prior to that and I purchased a data logger and ran that for a while to generate a history. I also looked into selling it, trading it and just about everything in between.

Cheers,

dvzzz · December 7, 2019

thanks, what parameter did you log and what data logger? Picoscope?

2 hours ago, ArrowsmithPML said:

Mine was recorded as similar. #17-NA-166 and pico scope analysis done with spikes to 4.8, then 2.8 and then 1.8 at times - very erratic and unpredictable.

Anyone that has this vibration issue should really do everything they can to address is.

I was advised to run a few tanks of premium fuel - which I did and noticed a slight correction but it never went away. We had 3 of the 8 injectors replaced prior to that and I purchased a data logger and ran that for a while to generate a history. I also looked into selling it, trading it and just about everything in between.

Cheers,