GMC Yukon XL - engine/trans stuttering at 1250-1750 RPM

Maintenance/Repairs
1

Hi all,

I have a question regarding the stuttering of my engine at in the range of 1250-1750 rpm and potential sources of the problem. Vehicle specs below, followed by the problem in more detail.

Make: GMC
Model: Yukon XL 1500 Denali 2WD (8 Cylinders J 6.2L)
Year: 2018
Mileage: approx. 96,000

The problem is fairly specific and only occurs when the engine is in the RPM range of 1250-1750… which is generally when driving in the range of 30-50 mph. It’s when I’m cruising at a consistent speed, the engine starts to stutter and shake. This isn’t a “once in a while” issue, it’s every time I’m in that speed and RPM range. I’ve had the GMC dealership look at it, and they just brush it off. The stuttering occurs during cruise control too, but less frequently because the car doesn’t seem to hover in that RPM range. I did get the engine icon to light up when I purposely kept the car in the range and just let it stutter for a while. I looked up the problem and it said engine misfire. I’ve had a local auto shop look at it and a friend of mine who’s a car geek, suggested maybe switching the spark plugs for the misfire, which I did. It was an inexpensive try, but it didn’t fix it.

From my research, I’ve seen mentions of somewhat similar issues with the transmission or the fuel injectors, but the symptoms of those problems are close, but not the same as what I’m experiencing.

To be clear, the car does not stutter above 2k RPM at all. It runs perfectly.

I’m reluctant to just throw everything at it since the car is out of warranty and I’m not interesting in spending a ton of money on a new transmission if this is a more simple fix. Worse, I’m worried that it’s a sign of something more serious and I should sell the car now before it becomes a much more expensive issue.

Ironically, I also have a 2019 Cadillac CTS-V and I have the exact same problem, but only far less frequent and it’s not nearly at noticeable. But it’s exactly the same problem with consistent speed in that 1250-1750 RPM range.

Both cars are GM in nearly the same model year, so I’m wondering if this is a common problem with GM cars using the same faulty/crappy components.

Any thoughts on what this could be?

2

What you might be feeling is torque converter shudder.

The next time this occurs. keeping your right foot on the gas pedal, take your left foot and slightly step on the brake pedal.

If the shudder goes away, that’s what it is.

Tester

3 Likes
3

Very common issue. Google “GM Service Bulletin 18-NA-355”

4

As I read through I was also thinking of TCC shudder.

But how did you get to this?

I.e. the engine light lit up, you had the codes read and found a P030 code? Or did you just do some generic code on stuttering and engine light and found a lot of references to misfires? If you didn’t get the codes read, get the light to come on again and have them read. Many auto parts stores do it for free.

Mostly, I thinkk you have TCC shudder tho’

5

How many times have you had the transmission fluid changed? Based on the mileage, I’d expect 2-3 times.

Sounds like a fluid change also works with the TSB mentioned.

1 Like
6

If the shudder goes away as Tester mentioned while pushing the brake pedal just enough to turn on the brake lights…

We used to do back to back flushes and change the filter and finally add a tube of LubeGard Instant Shudder Fixx, worked pretty good… And use the correct ATF NOT a one size fits all ATF…

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7

You guys are amazing!

For the error code: I don’t remember which it was specifically, but misfire was where it ended. I was in cruise control and I dialed in the speed to get the stutter to happen. I let it progressively get worse over maybe 10 seconds. The car ended up disabling cruise control and that’s where the engine error code came from.

For transmission fluid, I don’t know how many changes I’ve had, but I’ve maintained regular service through the dealership and followed the recommendations.

I need to get the car serviced soon, so I’ll make sure to bring up the torque converter issue.

Thank you,

Daniel

8

Based on the normal GM recommended transmission service I guess your total number of transmission fluid and filter changes on both cars is …none.

GM calls the fluid lifetime. Most posters here change at about 60,000 miles and some much less. You might want to have the dealer check if it has ever been done and insist it be done because some dealers will resist and assure you it is not needed.

1 Like
9

+1
Car manufacturers have been in a virtual “race to the bottom” for quite a while with their claims that their vehicles require minimal maintenance. I actually had to argue with a Toyota service writer when I asked for a trans fluid change. He kept insisting that the fluid was “lifetime”, which is the same ridiculous claim that the mfr makes.

Whether someone has a “conventional” automatic transmission or a CVT, changing the fluid (and filter) every 30k-40k miles is the best way to avoid trans problems at a later date.

1 Like
10

With poor running in a narrow RPM range and a misfire code, one place to look is the TPS Throttle Position Sensor. See if its resistance changes smoothly as you move the throttle through its range, especially its position when the misfire happens.

11

TCS sort of feels like engine misfiring, but that is a different problem. It’s possible to have both TCS and engine misfiring of course. If your shop says your car posted a diagnostic code for engine misfiring, suggest to start there. Engine misfiring may damage the expensive to replace catalytic converter otherwise.

The typical diy’er diagnostic process for misfiring is

  • visual inspection of ignition and fuel system
  • swap spark plugs, fuel injectors, ignition coils to see if misfire follows the swap or not.

A pro-level scan tool in the hands of an experienced mechanic will get to the cause faster, so that’s a possibility, hire a shop to do the diagnosis. Then you can replace the suspect parts yourself if you like.