Thanks for the reply, maybe we can eliminate some things: the car is a 97 model if that makes any difference - non-turbo mileage - car has done less than 60k injectors - I have tried a dose of injector cleaner, made no difference I have changed air filter, old one looked ok too, also did fuel filter fuel consumption is higher than I would have expected engine sounds like it is running ok (to my diesel-ignorant ears) starting is ok, in fact less smoke when cold (this points to a cumulative air problem?) TIA