my 03 doblo cargo van jerks between 30 & 40 mph in 4th gear jerking goes off when put in 5th gear, can anyone suggest what might be causing this, thanks

Mine does the same. It is a 1.9d and it would seem that it is missing at certain revs. I have had the car for a couple of years now and have not managed to put a finger on what is causing this though :-/