Volkswagen: car jerking, coolant temp, throttle valve

Question
car jerks now and then and also when i change from 2nd to 3rd it stalls a bit and then goes,same for 4th to 5th,and when i accelerate on 5th gear it seems to starve for fuel,it like wants to cut-off.what could be the problem as i have put in an injection cleaner thinking there could be dirt in the fuel system? golf 3 gti,1996 exec.did run into reserve a couple of times!

Answer
we have come across a few occasions where the throttle valve is faulty. firstly, try removing the intake pipe from the air filter / air mass meter to the inlet manifold. by hand open the throttle valve, and check to see if is clean around the flap, as if it is chocked up with oil and carbon it cannot work properly. if it is dirty, try cleaning it with thinners. also you could try replacing the four pin coolant temp sensor as this can cause similar problems. if both of the above do not work, then it is more than likely that you may need a new throttle body, but this is a last resort due to cost. before replacing this component i would have the car code read at a specialist or main dealer just to be sure there is nothing else.