I agree with James but................. lol......................it's certainly worth using a cleaner like BG244 first just in case it's something that can be cured without expensive treatment. For example the old MK3 Mondeo TDCI was well known for its cold weather blues and there are countless people who reported smoke and shuddering etc and it was usually down to needing a clean out of the fuel system.
When I had it with my old TDCI I used BG244 and the symptoms stopped and never came back. The car would cough out smoke in the morning and shudder bordering on stalling. I used it once a year after that. You can get microscopic particles or glazing in the injectors which causes rough running and can be cleaned out with this stuff. Don't bother with cleaner you see in the shops as it's not strong enough.
However, it won't cure damaged or worn injectors as James says. Injectors no longer last the life of the car and should be seen as consumables. All I am suggesting is you give cleaning a try before resorting to more expensive remedies.
- jeebowhite likes this