im not sure of whats going with the car right now, here's the problems, this only happens when the car is in gear and after i have driven for about a half hour or more the car start to stall, and buck heavily after about 3500rpms, the runs ok, below that. it doesnt matter what gear its in. i dont think its a engine problem. because when im in neutral and rev the engine everything is fine. im thinking it could be that my clutch is slipping. can anyone else help me please.