I was driving along the motorway and the car started juddering and losing power. Was recovered by the AA to our garage but they can't findout what is wrong. AA man suspected an injector had gone (it is a diesel) as there is white smoke being emitted from the exhaust and it sounds like it is mis firing. The garage is now saying it could be a fuel pump. These are really expensive (I think) and was wondering if anyone else has any ideas. There are no warning lights on. Cheers