50th year

Maybe Its the A8 I am not use to. Its hard to put into words but the car is jerky like it is missing but its not. Kinda like when a car is driven before it warms up. This is a 2017 GS . All my previous corvettes were always smooth on take off. Anyone know if this is normal for the c7?

mountainears

Any chance it's switching from V4 to V8 at the time? There's a screen on the DIC where you can watch for that (I think the one that shows your current MPG)

50th year

It happens under load so I don't think the v4 comes on. The trans works great at WOT. It also happens in Manual. I hate to take it to the dealer and have them tell me its fine. I did notice it had 30 miles on it when I picked it up so maybe the were trying to figure it out. All my other new vetts had only a couple of miles when I picked them up.

mountainears

Some vettes are taken out for QA runs at the factory, it will usually come with a slip of paper saying that (they put it on the test track). All others should have 3-5 miles on them, that's it. More than that it had been test driven or something.

There's some talk on the forums about some warble and other issues with the drivetrain on A8's, but that usually comes after a bit of miles from what I've been reading. May not be urgent to take it in for it. Not sure how many miles you have, if you've done your 500 mile oil change yet? If not, maybe ask them about it then, not a special trip just for that.

I'd also take it to a very reputable Corvette dealer as well, one that has some Corvette certified techs. Look in the regional forums for your area and find dealers that are recommended.

50th year

I ordered this car so there shouldn't have been any test drives. I already did the 500 mile oil change. It doesn't feel like a wobble. It just feels like its surges back and forth when driving. Driving me nuts

NSC5

If your car is chosen for a quality audit OR if there is an issue after it comes off the line it will get those additional miles whether it is a specific customer or dealer stock order. One of my GMC pickups went through the audit and it had 22 miles on it when I took delivery, it was a customer order for me. As I recall my Z06 had less than 2 miles on it but it was a museum delivery in March 2016.

GM used to include a note about QC audits with the paperwork for vehicles that went through the process but I think that practice might have ended.

Does the miss feeling occur under moderate to heavy acceleration? Does it occur when the transmission is set to manual mode? Also there have been reports since the start of production of owners finding one or more spark plug leads not properly seated on the plug. Once it comes off it will create an obvious miss and set a code but if one of your leads is loose it may be intermittently not firing cleanly.

50th year

Thx
I haven't opened the hood yet so I will check the plugs. The miss feeling happens under light or moderate acceleration. The fact that it had 30 miles on it and maybe an issue at the factory is worrisome.

NSC5

I would think moderate acceleration would be enough to ensure it doesn't go into V4 mode but put the transmission into manual mode to be sure as a test since this (or a Range anti-AFM module) are the only way to keep an automatic equipped C7 from going into V4 regardless of driver mode setting. I keep a Range module in my Z06 to prevent it from going into 4 cylinder mode but even without it a Z06 rarely goes into V4 but the LT1 engine will go into V4 mode under a much wider range of conditions.

It is quite possible your GS went through a quality audit instead of being pulled for a specific issue. A sample of production is chosen for the quality audit and the cars that are part of this are not chosen because they had an issue.

mountainears

Yea, that would maybe be a good test. Drive around in manual mode for awhile (you may never go back) and see if you have the same issue.

I have a range technology AFM as well for my 2017 GS, throws engine codes all the time so I stopped using it. I don't think they have the 2017's figured out yet.

davepl

Don't bother checking plugs and wires and all of that, there's no misfire. If there WAS a misfire, the OBD2 systems would detect it and light the Check Engine light. Cylinders not firing is a big deal for emissions, and hence we benefit from VERY sensitive misfire detection as a result. I believe the crank position sensor can actually track the acceleration/deceleration of the crank from power input and detect when one is missing.

So it's more likely something like the TCC slipping when trying to engage, something like that. I doubt the motor has an issue, as it'd be flagged quickly.

Dave

50th year

thx dave
I will mention the TCC slippage might be the problem when I take it to the dealer. I hope they have the ability to check that and adjust it if its needed

djnice

When you say it happens in manual, is it happening only when you shift? Are you observing rough shifts? Does it happen in all gears? As far as checking if your in V4 mode, you can scroll through the information screens and there is one that shows when your in V8 or V4.

50th year

It happens in Manual as well so I doubt its the v4 to v8 problem. It might be the TC or Trans slipping. Best guess so far. A day at the dealer Great!

50th year

I just got back from running the car around the neighborhood in manual and did not notice as much surging and such so I guess It must be the a8. It looks like manual operation for me.

NSC5

Dave,

I thought the same thing until I noticed a little roughness at times in my 2008 CTS (3.6L DI). I ran a log on the engine and noticed one cylinder would randomly show a few misfire events BUT it was below the threshold to set a code. Apparently random misfires are not that uncommon and to avoid "nuisance" setting of a DTC nothing happens until the threshold is exceeded. In my case a coil pack was on its way out on the affected cylinder and replacing that took care of the issue; I am sure if I had let it go it would have degenerated to the point where misfires would become frequent/consistent enough to set a code. I was surprised at the time to see misfires detected with no code and that is when I learned about the threshold criteria to set a code and previously thought that misfiring would instantly set a code.

davepl

Thanks, wasn't aware there was a threshold of misfires that it had to cross before setting the MIL, good to know!

NSC5

You are welcome Dave and it surprised me also. I never found any good information as to what the absolute thresholds are to set a DTC and if they vary by engine.

Higgs Boson

TCC is a good guess, that could be it, under partial load, the TC is locked and will unlock in the 4-5K RPM range, if you are getting to that RPM, depending on pedal position, it could be acting weird. I don't like the stock TC settings at all in the A8.

It could also be overfilled oil getting in the intake, that was a fun issue for a while, maybe on the MAF.

could be a vacuum leak where the fuel trims are compensating at idle and lower loads but if you are giving it enough load when it happens then they may not be able to correct.

quite a few other suspects. better to have driveability issues like that diagnosed in person.

17BLKGRNDSPRT

I had the same issue with my car at 6 miles 2017 1LT Base A8. Dealer says it needs to be driven. No codes just felt like it was hesitating and jerky sometimes. At 500 miles it started to make the warble sound. Thought it was the exhaust until I searched this forum - which suggested it was the differential. Took it to the dealer they said the fluid had metal shavings and differential will be replaced. Got it back Friday immediately felt like I had a new car. Runs smooth and no more warble.

djnice

That's interesting you picked up on a problem immediately. Probably was nothing the dealer could do to keep it from toasting the diff. I wonder what was the root of the problem in the diff?