1. KiwiTerrano

    I suspect the problem is actually with the injector pump. These are known for having problems with the plunger solenoid as they age, which causes driveability and idling problems.

    As first steps though, I would replace the diesel fuel filter (in the engine bay), run some diesel injector/fuel system cleaner through it, and check the fuel pressure from the in-tank lift pump. If this isn't funcitoning well then it will flog the injector pump out faster. Also check you haven't got massive water/crud contamination in your diesel.