My automatic 2000 Neon is having a shifting problem. When it starts to go, it will barely move, then screech the tires and shoot off. Feels like it's starting in second, lugging, then downshifting into first when it gets more throttle. It also randomly shifts up and down sometimes while driving down the road, quite violently. I know the car has a bad TCC solenoid, but I thought that had to do with downshifting while coming to a stop. Also, I can't see how this would matter, but it all started when I got it back after having the A/C compressor replaced. Any ideas?

 

TCC is torque converter clutch solenoid. If its locking up and unlocking, it can cause the symptoms you describe. Have that diagnosed and repaired. Could be a bad TC also.