Dealer not honoring warranty work..2018 5.3 Yukon issues

[smokey_mountain]

I actually bought the water from Costco just for the test. I use RO at home and do not own bottled.

I don't really see how anyone could say they can't detect the engine running at all. I was going to do your water bottle test in a few trucks including my own (2008 and 2012) just out of sheer curiosity but I don't drink bottled water so I've got to get a bottle for demonstration purposes.

 

[smokey_mountain]

guys in another thread are reporting that Gm raised idle on 2020 trucks to 700 RPMs... interesting.

 

[smokey_mountain]

it is colder today in NC sub-freezing and on the drive to work this morning in D it was shaking more than usual, what it is even more interesting shaking got worse/stronger in P now. P raises RPMs slightly but it seemed to make things worse, before P was better than D.
I put K&N drop-in filter into a stock airbox last night just to try. I knew it was not supposed to change anything and I do not think it did, but this change with weather is puzzling, this truck is a mind-bender to say the least.

 

[smokey_mountain]

I am curious if there are folks here who are familiar with Picoscope process for this TSB 17-NA-166. Truck shakes very noticeably when cold and I would like to find a way to measure for this TSB. From the reading I have done, Picoscope measurements are hugely sensitive to the mounting location, method, etc. I would like to attempt to convince the dealer that my truck is a candidate for 17-NA-166.

 

[smokey_mountain]

Local mechanics both quoted the job cost to replace front engine mounts - $1100-1240 for the labor (11-12 hours) and $420-$510 in parts, they only warranty parts that they source. So this is a quite bit of change to get this TSB 17-NA-166 done paying out of pocket.

I have spent a lot of time studying Picscope measuring procedure and talking to other mechanics and margin of error is so significant on these tests that the whole notion of Picoscope being the criteria for the decision is highly questionable. It takes 1+ hour to setup the Picoscope and then another 30 mins to calibrated for different types of measurements. Basically local former Ford Master mechanic told me that if you want to can get Picoscope to register or not register and you achieve all that by just slightly adjusting the position of the scope. I highly doubt that dealers will be doing it intentionally, it is simply too time consuming to measure properly.

 

[91RS]

It doesn't take anywhere near that amount of time to setup the Picoscope unless you have no clue what you're doing. I thought the last dealer you went to measure it with the Picoscope per that bulletin and it was below spec?

 

[smokey_mountain]

What I have learned that the only Pico that is approved is CH-51450-A. None of the dealers confirmed if they indeed used CH-51450-A. Another concern was that single-axis is measuring 10-12% less in E1.5 so only tri-axis should be used. I have no way of knowing if they used tri-axis. Given that one measured 1.2mg and another 1.5-1.75 it is not completely out of the question that simply mounting error creates big enough error to give incorrect reading and not in my favor. I wonder what would they do if I had a GMC performance exhaust, what I have heard that exhaust will cause all numbers to rise considerably.

At this point, after 3,000 miles in this truck, I have a book case from this TSB, idle is rough after extended driving or after hard acceleration, no codes, all systems check. @91RS You were spot on with your suggestion that this is engine mounts. Independent GM tech also after looking at all data suggested that mounts is the most likely culprit here. My truck was manufactured in 06/2018 and falls into the TSB brackets.

The Medlin GMC dealer is willing to help, they are genuine but they are saying until you exceed 2mg GM would not pay. I spent 1 hour on the phone today with BBB Autoline and GM Lemon Law team, but GM is saying we understand you have the vibration but it is not bad enough to get the TSB performed. Lemon law does not apply to my truck as it was titled to GM before I bought for 4 months.

2mg is GM self-appointed threshold to prevent flood of engine mounts replacements. As we learned it is not a $100 repair, I understand why 2mg is there, it just does not solve my problem at the moment. If 2mg was indeed acceptable I would not have my truck shaking at every traffic light.

It doesn't take anywhere near that amount of time to setup the Picoscope unless you have no clue what you're doing. I thought the last dealer you went to measure it with the Picoscope per that bulletin and it was below spec?

 

[91RS]

I'm almost positive the Picoscope is a required essential tool for all GM dealers. The three-axis sensor is not required but the bulletin clearly states how to measure for this problem with the one-axis sensor also so it isn't that difficult. One thing you should understand is that you are talking to service advisors, not the tech(s) actually working on your vehicle. No offence to any service advisors out there by any means because the techs don't want their jobs but they generally only have a rudimentary understanding of what goes on in the shop, most of them likely have never even seen the Picoscope.

 

[smokey_mountain]

Yes, I was only led by this statement in the TSB mandating specifically CH-51450

 

[smokey_mountain]

Quick update for those who follows this thread. I am on the 3rd tank of regular 87 BJ's and before Sam's Club gas. Absolutely zero change to my shaking and rough idle, not worse, not better. Exactly the same. I can say with confidence that in my specific case fuel is not a factor. Gas mileage per my computer is 0.4 MPG less on 87 than on Exxon 93 but this is not even accurate as weather changes from subfreezing to 76 degrees in NC within 24 hours and I have thrown out K&N drop-in filter and replaced with the OEM one.