TD4 Rough Idle

My MY04 Freelander TD4 (Auto) runs rough or misses at idle. Problem is inconsisitent - sometimes its fine while other times its rough - to varying degrees. When revved in neutral, while idling rough, it produces a white/blue smoke which clears after returning to tick over. It drives ok, generally without smoking, power is good and it is difficult to tell if it is missing whilst driving. It has only done 80,000km but I have been reporting the problem to dealer since about 60,000km - last time they had it for a week to diagnose and it came back OK after reprogramming but has since lapsed. Have changed fuel pressure regulator, fuel filter, breather hose etc. A volume test indicated it was overcompensating the fuel but this was dome twice with a different injector at fault each time.

Only other fault has been intermittent as well - ABS, Traction control light come on and cruise control wont work. Thought this was fixed with a new switch (brake pedal pressure switch??) but still occuring also. They don't appear to be linked as they don't necessarily occur at the same time but if it's electrical they could be linked.

I have booked it back into the dealer but this is driving me mad so I thought I would investigate myself so I could talk through what they have tried - have seen some similar problems on this forum but any ideas to take to the dealer would be appreciated. Thanks. Wade.

My initial approach would be a careful check of all wiring between the injectors and the engine management ECU. Occasionally these harnesses fail internally.Good luck.

another injector problem i think

Now have it back from service and dealers claim it just needed a software upgrade. Definitely running better but I'm yet to be convinced it's 100%.