[Piggy]

I am still having a problem with my 09 2LT with the ecotec. I have just over 17,000 miles on it now. Sometime around the 3000 mile mark I noticed an occasional shudder coming from the front of the car when accelerating through 12-20 mph. I can also sense something out of balance at around the 60mph and up mark but this is minor in comparison to the low speed shudder. This has now grown into a very annoying intermittent problem as I spend a lot of time on the hwy in stop and go traffic and at high speeds.

It does not seem to happen when the car is cold. Sometimes takes 15 min to 30 min to show up. It comes in varying degrees of severity. At its worst there is a very noticeable 6 or 7 pulses or shudders which can be felt in the steering wheel and through the seats of the car.

If I keep it in 1st or 2nd via manual mode it still happens. When in Auto the transmission functions smoothly through the shudder when it occurs it.

The engine is not running rough, it powers smoothly through the shudder with no noticeable rpm dips peaks. However it does seem more frequent and stronger when the engine is under load like going up a hill or starting with the wheels turned.

I have had this car at the dealer several times for this issue including letting the tech take it home for the evening so he could experience it in traffic. They acknowledge that they can feel it.

So far they have balance the tires, done an alignment and reprogrammed the transmission all without fixing the problem.

I thought I would check again to see is anybody else with a 4cyl 6speed is having\solved this issue?

 

[DrivenDaily]

Intermittent faults are always the hardest to track down. Two things come to mind: ABS and EPS (elec. power steering).

All models come with ABS and if it activates it could easily do what you describe. The ESC system could be sending a false signal, or a sensor could be faulty, or something else in the ABS could be at fault.

EPS is only on 4-cylinder models. An issue there can cause symptoms like you describe though it doesn't seem as likely as ABS.

Did your dealership mention or check either of those two systems? Also, why can't they provide a free loaner vehicle for you seeing as you're out of your car for so long? If this happened to me they'd have to, since this is my only car.

 

[Starship]

If the ESC is kicking in, the ESC light should be on in the instrument cluster during these incidents. If it were the torque converter lock-unlock shudder, the TCU flash(es?) should've helped.

Seeing how the problem was noticed after 3000 and now only when everything is warmed up, it may be something mechanical inside the transaxle. A worn bands/clutch packs (involved in 1st and 2nd) or internal fluid leaks can cause shuddering (repeated slip-grab). So can worn torque converter clutch. It sounds like the dealership is doing everything but tearing into the transaxle. They probably didn't even look at the condition of the fluid. If Piggy hasn't done already, I think it's time to get GM actively involved.