it is not slipping out of gear?
there are a few things that can be wrong with the info ya gave..
Ignition timing is incorrect or is not working right(for both probs)
dirty fuel injectors (this can be your other problem too)
wouldn't hurt to check your throttle body bore, use carbeurator cleaner and a toothbrush. (this is for both)
check your air filter, timing belt, check for vaccum leaks (hissing sound), leaking head gasket.. and check your engine oil, coolant level, and other fluids...