Thread: 2008 Grand Prix jerking, shudder at low RPM's

Hello everyone

I am trying to figure out whats causing an odd issue with my car, its the N/A V6. It seems that when in 4th gear and applying steady on the gas pedal if between 1000-2000 RPM's the car begins to jerk and or feel like its shuddering, miss firing. Its fine in the other gears and when accelerating around the same range. It has power and idles fine, no check engine light on. If I have the car in park tho and try to steady the RPM's between the 1000-2000 range, it will start to flutter and then drop then hold then drop all slowly. Prior to this happening I replaced the battery. Also changed prior to this happening was the ICM, all 3 coil packs, plugs, wires, and air filter. I just cleaned the MAF sensor and tried to clean the throttle body but couldn't really because the car was still to hot. I tried disconnecting the battery and resetting the car and that didn't work either. I know the 06-08 Grand Prix's are drive by wire and I am starting to think its either the TPS and or the gas pedal itself that is acting up. The car seems to do it all the time for this week so far but not constantly, its sporadic. I thought I would ask and see what anyone else may think. Sine the car hasn't thrown a check engine light, im at a loss.

Thanks for the help.

Originally Posted by GMR Badass

Do you happen to have a scanner or access to a scanner.

Sounds like your TCC (torqu converter clutch) is locking and unlocking when it shouldn't. Put the gear shift into 3rd gear and drive around again. This time in the same rpm range that you're noticing the issue and see if it happens while you're in 3rd gear.

I did do that earlier today and it didn't do it, car was perfect. I have read that it could be the TCC but I figured if it did it in park and getting the car to act up that it wasn't the TCC. How hard is it to replace this in the newer Grand Prix's? I know on the earlier ones you have to lower the trans to get the side cover off. Is it the same? The car has 145,000 miles and its really my girlfriends car. Would a trans service help? I told her worst case it needs a transmission, but the car has never had a full fluid or filter change. I would like to do so but am afraid that it will finish it off. I have only removed about 5 quarts and added new fluid.

I don't have a scan tool, I had auto zone scan it to see if the car had any pending codes but nothing showed. I'm gonna have to find a shop or the dealer that can scan it and run a further check.