M555SUB

Hi fellow scoobers, i need help for my other car which is a vauxhall astra 1.7dti 2002. It runs fine for about 60 miles without any problems, then engine cuts off. It restarts but instantly off again. I leave it for half an hour or so, then its on without hesitation but cuts off after a few miles, i turn it on and keep revs high when stationary so it dosent turn off.
mechanic hooked it upto a comp, few fault codes came up but mechanic cant seem to link any of them codes to the problem. any hlp appreciated Thnx