Major RPM flutter 2007 2.2L 4T45E

[rodeo02]

Anyone else experiencing a flutter or RPM bounce when the transaxle shifts into 4th during moderate acceleration? This is on my 2007 2.2L, 4T45E equipped Cobalt. It seems to only happen once fully warmed and I'm not positive if it's happening on the 3-4 upshift or during torque converter lockup in 4th. There is no check engine light and other than that, it runs flawlessly and has been perfect. I have heard of one or two other 2007 owners with the same concern. No issue was found by their respective dealership service depts. I'm also not exactly sure if this is a throttle by wire problem, transmission problem, etc.. Basically the tach will bounce up/down about 500RPMs at about half second intervals during what feels like the 3-4 shift. You can hear it and feel it as well.

Joel

[cmhj2000]

Hey again Joel,

Not one I'm familar with but will investigate.

[rodeo02]

Hey thanks bud. Yeah, I've got this posted on two other boards so far. Not a single idea as of yet. It is weird. Basically the engine goes Rrr...Rrr....Rrr...Rrr.. & tach bounces about 500rpms until I change throttle position. Then it smooths right out. You know how it goes. W/out something broke or a code, taking it to a dealer will be useless.

Joel

[cmhj2000]

Ya I hear ya'. Stuff like this can drive you nuts.

Had a guy with Cummins diesel in an 02 Navistar that had a DBW system do something similar to this. No codes, drove me crazy. Replaced the TPS and the issue cleared.

[rodeo02]

Just an update; I'm just under 12Kmi now and the torque converter oscillating in/out of lockup issue still exists, so I finally made an appointment and dropped the Cobalt off at the dealer. They had it for the day and drove it quite a bit. Their Techs were able to duplicate the concern. Apparently "GM Engineering" is aware of this issue effecting ~2007 Cobalts with the 4T45E AT. GM says it's a software problem that they are still working to debug. The service writer admitted it was way over his head, but it had to do with "serial bus #1, module 8" (something like that). In the meantime, what they did for me was download the latest software to my PCM and cleared the adaptive shift logic that the trans learned itself into. For now the problem is gone. It glides into lockup nicely w/out oscillating in/out. No cost to me and I was actually very impressed with how I was treated by this GM dealership. Basically the conclusion was; If the problem comes back, call them to see if the latest/greatest software is available. They will clear the shift adapts for me until a patch has been established.

[cmhj2000]

Hey Joel, thanks for the update. Soemthing I'll talk about with my dealer in a couple weeks and see what he says.

Mine is still working fine. However, I must admit the wife took it away from me a couple weeks ago. Can't say as I blame her though.

[cmhj2000]

Joel,

Ever get the butterfly issue figured out?

[cmhj2000]

Originally Posted by cmhj2000

Joel,

Ever get the butterfly issue figured out?

Darn edit feature didn't work

What I wanted to ask is the flutter issue still gone?

[rodeo02]

Yes, so far so good! I'm at about 16500mi right now, so that puts me at about 4500mi since my dealer cleared the shift adapts. She still shifts perfectly and no crazy bounce. Thinking back, the problem originally cropped up somewhere around 3-6Kmi IIRC. Keeping my fingers crosses it doesn't come back. Off topic, but with 5w20 in the sump and the tires pumped up to 39-40psig, i've been averaging 32-33mpg per tank for a cpl months now. Pretty sweet!

Joel

[cmhj2000]

Glad to hear that Joel.

I also made a switch to 5W20 Amsoil XL in my balt. It seldom sees the highway and has very little stop and go driving when it's real hot so I'm not worried.

So far the wife says she picked up almost 1 MPG on the DIC, which is more than I expected. I think you know about my 2 cycle oil experiment, which is giving her another .5 or so MPG.

BTW I'd really like it if she gave me my car back.!!!!! Stuck driving her Optima.

[rodeo02]

Just an update.. I'm at 25Kmi now and that transmission gremlin is thankfully still gone! All it took was clearing the shift adapts. I never did hear if GM has actually addressed this software concern or not. Then again, I haven't heard anymore complaints either.

Joel