I have a 1989 Golf Cab GTi. Recently, when going uphill, the car stutters when you change gear from 3rd to 4th, and likewise to 5th. This doesn't happen all the time, but occasionally it can almost feel like the car is going to stop completely. For a few seconds there seems to be no power/acceleration.

When I first bought the car it had a similar problem and I was told it was the pressure in the fuel injection pump which needed adjusting. Could it be the same problem again?

I have also noticed the car needing regular coolant top-ups recently but I'm not sure thats related. It has never ever over-heated.

Thanks