2016 All Terrain X

I wish I had some positive news to report. I am having major issues with my 2016 GMC Sierra 1500 All Terrain X. Started have excessive vibration during idle and up to about 1700 RPM's when driving. Vehicle has nearly stalled out on me several times when accelerating from a stop at a major intersection. It feels like it's flooding. GM does not have an ounce of clue about how to fix this problem. The only reason they would change the motor mounts or shim the motor mounts is to change the frequency so the driver does not feel the vibration. They are only trying to correct the symptom and are not addressing the root cause. My vehicle has approximately 20,000 miles. The first time I noticed the excess engine vibration was around 100 miles. The dealer told me it was normal. I argued with the dealer and said that is not normal on a vehicle that lists for around $50,000. Obviously I did not pay anywhere near that price. After fighting with the dealer they agreed to get their "top" mechanic on this. After their top mechanic assessed the problem he was told by GM to shim the motor mounts. I do not think I have ever laughed so hard in my entire life. That's like having a refrigerator with a broken ice maker and the technician telling you to change the wheels. The third visit consisted of a different dealership. I was fairly impressed with these guys. They kept my car for almost two weeks. The lead mechanic drove it home a few times and experienced all the conditions I had been getting frustrated over. Along with the low rpm vibrations I was also experiencing transmission shifting issues. My truck has the 8-speed transmission that I believe is built by ZF Friedrichshafen and is a joint venture between Ford and GM. They reprogrammed the transmission and replaced the motor mounts on the engine. When I picked it up from the dealer and first drove the vehicle I was blown away. I thought to myself that my nightmare of a truck was now my dream truck. Less than 100-miles later all of the issues returned. I was quite upset. This third visit was around 13k miles. The truck has never displayed a check engine light. I decided to drive the vehicle for at least 5k miles before taking it back to see if a check engine light would eventually come on but it never did. At around 20k miles I took it to a third dealership and the only thing they could find was a new update for the transmission programming. They reprogrammed the transmission and said everything else was normal. The vehicle is now vibrating worse than ever before and is going back to the second dealership that actually had it fixed for about 50 miles. We know the motor mounts, whether shimming or replacing is not the fix. This just happens to be one of the cheapest fixes that they could perform. I would imagine a good percentage of customers do not return after that repair has been performed because they just decide to deal with the problem and that makes GM think this fix is working. It did not work for me and I would imagine it to be hard to find someone that had this problem permanently corrected by replacing the motor mounts. Lets see what they can come up with on the fifth try.

I have a 2016 GMC Sierra All Terrain X. I have the same vibration issue that started almost immediately after purchasing the vehicle. It's been in the dealership four times and is no better than when it first started. The reason they are shimming the motor mounts is the change the frequency of the vibration so you don't feel it as much. They hook the vibration meter to a bolt that holds the seat down and shim away until the vibration lessons. Problem with this is it comes back because the root cause was not corrected. Most mechanics nowadays are only capable of remove and replace. If the computer does not tell them what's wrong they have no clue how to troubleshoot. Still having a problem and I'm getting ready for a fifth visit to the dealer. The way I see it is that there is the possibility of three different things that could be causing this. An air leak, a vacuum leak or an electrical short. If it's an air leak or a vacuum leak it's not very big. At idle or slightly above idle the leak is a larger percentage of the total air and fuel coming into the system. When RPM's are elevated the leak is a smaller portion of the air and fuel coming into the system and is virtually undetected. I also think it might be a problem with the way the vacuum system is setup. The system measures vacuum inside the manifold as well as out the manifold. If one system is using gauge measurements and the other is using absolute measurements it could cause problems at low RPM's. A gauge measurement is a linear equation and an absolute measurement is a quadratic equation. The bottom line with this is that the small differences in the method of measuring would cause problems at low RPM's but would be disguised at high RPM's due to the increased volume inside the manifold. The third issue of it being electrical would almost certainly cause the check engine light to come on so I have not gone down that road yet. Anyone else have luck getting their rough idle fixed?