Mercedes 270CDi advice

[phil350]

Engine juddering terribly at idle.
When selecting drive car again judders forward - once accelerating everything OK

Have tried Injector cleaning fluid without much prolonged success

Any thoughts advise would be most appreciated.

ps should the injectors need replacing do you need to replace as a full set (bearing in mind the car has covered 55K) - is this something i could easily do myself and where is the bets palce to order new injectors i.e. good quality but not necissarily at top prices.