Looks like I'm experiencing the "not so uncommon" issue where the vehicle shudders under particular circumstances.

2022 Stingray Z51 and just crossed 10k miles on the OD ...

1st time I noticed it, I honestly thought the road had washboard pavement on it. Going down the highway, steady state, and just applying throttle to maintain 70mph or so, while going up a slight incline. This is the most common symptom I experience, and have been for the last 2k miles or so.

Another symptom was accelerating up a fairly steep hill on a 65mph road. I was accelerating from a stop, getting up to speed, with about 50% throttle pedal engaged. Then suddenly, the vehicle increased acceleration even though I was holding the throttle steady (and going up hill). The best way to describe this is like I was pulling a trailer with extra weight, and then suddenly the rope was cut releasing the weight.

The latest symptom is the same shuddering feeling I get on the highway, but it's now happening at much slower speeds. Still with light throttle application, but it can now make the vehicle buck and shake back and forth.

My initial thought was DCT, but now I don't think so. I'm thinking it is either the "lose spark plug wire" issue, or is the "sticking camshaft actuator magnet" issue.

Before I pull the engine sheer plate and check the plug wires, I figure I will hook up my HP Tuner's laptop and capture a log with the cam position sensor data. According to TSB 22-NA-080 (PDF attached to this post), the Camshaft Position Variance parameter should never exceed 4% variance. So if I can log this parameter with VCM Scanner, I should be able to confirm or rule out this as the cause. If the variance is 4% or less on a test drive where the shudder happens ... then I'll pull the sheer plate and check the plug wires.

 

Good Luck and please post what you find. I see several people on C8 FB pages have this issue.

 

So I pulled a few logs, and the shudder did not happen while logging. Checking the data, the cam position looks good (variance never went above 2.2*), so well under the 4* threshold the TSB calls out. I do see some random misfires here and there, but HP Tuners can often report misfires even when not real misfire activity. And since it's reporting them when I'm not feeling the shudder, I'm not sure that's the cause.

What I do find interesting is that I had to unplug the Carbyte AFM disabler in order to plug in my MPVI3 interface, so I could take logs with HP Tuner's VCM Scanner software. So I wonder if the methodology the Carbyte disabler uses is flooding the canbus with info, to trick the PCM into keeping V4 mode off, and this approach is causing a torque model fluctuation. I'll leave the Carbyte AFM disabler unplugged for the next week or so, and see if the issue comes back. If it doesn't , then I'll reinstall the Carbyte device and test again.

 

Feeling shuddering while driving your Corvette is absolutely not part of the ownership experience we hope to hear from any of our owners. Safety is a top priority for us and we take matters like this very seriously. We want to ensure this shuddering gets addressed as soon as possible alongside your dealership. Please visit https://s.chevy.com/support-request and fill out our support form with additional details so our team can get in contact as soon as possible. We will look out for your contact.

 

Thanks, my power train warranty is good until Sep of this year, and I also have a platinum Chevy Protection Plan extending beyond. But honestly, I trust my own diagnoses skills more than my local dealer, so will try to diagnose this myself before bringing it in (if it needs to be brought in).

If I end needing a warranty repair, I'll definitely fill out the support form before doing so.

 

Always interesting to me that on nearly every car forum of which a member, someone plugs in a tune, or gizmo, and then the car misbehaves. The owner then comes on the forum and asks advice on how to fix a problem that they most likely are the source.

Modern cars are complicated computers on wheels and one never knows what will affect what in the programming.

To the OP, Good Luck sorting, but start as you have, by unplugging every device you have installed, and go from there.

 

Yeah. The CarByte doesn't (can't) change the programming, but it sure can and obviously does interfere with the information exchange on the network. ( say obvious because it prevents V4). And nobody knows how it accomplishes that. It very likely monitors certain data exchanges, probably using hooks that are available to scan tools (in fact it will even function as a "full-featured" scan tool ), and then it must be injecting info, either via available scan tool hooks or something else. Its either preventing the command to enter V4 mode, or maybe preventing the car from responding to the command. But it prevents the activation of the evil, insidious, and much dreaded V4 mode. So there is that. I don't have one.

It will be interesting to see if unplugging it stopped the issue.

 

Yes, there are a ton of folks out there who have no idea how a modern car works ... luckily, I'm not one of them

There are a couple of standard methodologies companies use to accomplish things like what the Carbyte is doing. I'ce spent enough time snooping canbus networks on modern cars to understand what is happening here. The Carbyte is flooding the network with a particular canbus message to trick an ECM in the system into thinking a parameter is at such a range where V4 mode is not allowed. I'm not sure which parameter it is flooding, but if it's one which is used to modify the torque model when in V4 mode, then I can see how it could cause a torque model oscillation.

I do have a DLC (diagnostic link connector) snooping cable (ie: an OBD-II snooping cable), which I made when I was reverse engineering the canbus network on my wife's Durango. That said, I really don't have a desire to go to that depth here and will just leave the Carbyte out if it is in fact the cause. If it's not though, I'll probabyl plug it back in.