Whenever I’m going about 25-40mph in my 09 Pontiac G5 Base, the RPMs bounce up and down. As if I’m revving the car but I’m not. I’m not sure what this is but it’s really frustrating. If anyone has the same issue and knows what it is, let me know!
Providing it's an automatic transmission, my Layman's guess is either the torque converter lockup is having trouble staying locked up, or it's searching between 3rd and 4th gear. In any case, it's a transmission problem. Are there any codes thrown?
If it is an auto, I would agree with Dart on this. Quick answer if it is? Change the transmission fluid. If it's black and smells burnt, that's also a problem. The new fluid may help or hurt the situation if the damage is already done.