Good troubleshooting suggestion! I'm not sure when GM went with pulse-width modulation for the TC lockup solenoid, but that's where the problem lies with the ~2007s. Instead of a typical full on/full off TC lock solenoid like most 4T45s have, the newer ones use PWM, where the lock solenoid can infinitely vary it's speed/stroke. GM did this to 'soften' the feel of TC lock/unlock. If feels slushy and horrible if you ask me, espically when it gets caught in that nasty oscillation loop. You're right though, just varying throttle position or tapping the brake will stop it.

 

Tman- how did you make out with this? I've only put about 500mi on mine since they cleared the shift adapts. etc, but it's been perfect so far.

 

They cleared the "Taps" from the TCM so the bounce did disappear. So far I've only put about 200 miles on it. The serviceman claims that once the computer relearns how I drive , it will return. Lets keep our fingers crossed that they are really looking for a permanent fix, because I really like they way it picks up now when I kick her in to pass.

 

We've put a couple thousand on ours and it's fine so far...

 

Thanks guys. I'm hoping it stays away. I don't have a lot of faith in the supposed fix.

 

I have this problem too. I guess they carried the software over in '08.

 

I went to my dealership today. They cleared my shift adapts and referenced me to #PIP4314C for future reference.

 

I have a similar problem when sitting at idle. My afr goes into the 17's and the car surges and then it jumps to 13.5 then back to 14.7...


Still trying to figure it out...

 

Thats not a trans problem. That's an engine problem. Your O2 gauge is sensing a lean condition and the ECM is trying to correct it. The problem shouldn't be happening, meaning that one of the sensors further up the line (probably the MAF) isn't working correctly.

 

So after about 3or 4 hundred miles the rpm bounce returned. I called the dealer yesterday and spoke to the service manager. There is a case number opened for my problem and he called the GM engineering dept. They claim they are still working on re-writing the algorythm for the auto transmission control chip and it will be ready soon as a reflash. But what SOON means is anyone's guess

 

That sucks. I'm still bracing for it. I'm ~2000mi into the shift adapt clear (just under 14K total on the ticker) so far so good. Hard to believe GM hasn't come up with revised software by now. From the looks of it, this has been a known issue for close to a year. The way they are pumping out Cobalts, you'd think they'd be on to something.

Joel

 

This has happend since I bought the car. It never causes any trouble it's just annoying. I can't get the computer reflashed either under warranty because I don't have one.

 

Has anyone heard more on a fix?? They reset my shift adapts back in March but of course the problem came back. I was just in for an oil change a couple weeks ago but forgot to ask if GM had come up with something yet. If it wouldn't be for having to pass people on the hwy, I think I would have forgotten about the problem by now.

 

Dead thread BUMP

has there been any solutions to the problem yet? My '06 2.2 has been doing pretty much what these other guys posted.

 

I know this is an old thread but it saved me. I own a 2008 Cobalt which experienced a 300/500 RPM bounce or flutter around 1,500RPMs, usually shifting between 3rd and 4th, (torque converter lock in-lock out). I took it to Chevy and got the usual "could not duplicate"' no codes thrown, etc. I printed out this forum and finally got the service manager to look at it. He contacted GM. There are no TSBs on this problem but they had heard of it and said to replace the Transmission Control Module (TCM)under warranty. Worked like a charm.... no more problem.... so far two weeks.

If you have this problem, print this out and take it with you to your dealer.
Thanks to forum people!!!

 

Good luck, but my bet is on it returning.

 

So have you had the problem reoccur? I've been having this problem FOREVER and I desperately want to get it fixed. I do over 600 miles every 2-3 weeks and it drives me insane.

I've even considered replacing the TCC Solenoid in the transmission but I'm not even sure it would help. I have cleared the TCM Adaptives and it seems to get better for a while. The problem just comes back after a little while.

I'm running a 2006 2.4 L auto with a K&N short ram intake and a Trifecta tune. The RPM fluttering was happening before I got the intake and tune. I just want this fixed. Hopefully someone (GM) has found a permanent solution to this.

 

I got a Trifecta tune and it fixed the problem.

 

I have a very similar problem but my 2007 Cobalt is a manual. My car will surge and buck when I accelerate, hit a bump in the road or driving at a steady speed. I have had a few times when may car will bog down and won't accelerate at all. To fix that I down shift and pop the clutch but the tach will no longer work. It seems like when the tach quits working I no longer have the problem with the surging and bucking.

 

Wow. Bump.
Had the same issue discussed in this thread in my 2002 Chevy Malibu 3.1L V6 with a 4T40E. 130 000km. From what I read the 4T40 and 4T45 are very similar. I have to take the car to the dealership at some point for the unintended ignition key rotation recall and I feel like printing this off and going to ask a few questions while I'm there. Has anyone received this software update? Any other developments regarding this issue? Would very much appreciate any replies to this thread!