My wifes 55 plate D4D T3 started to mis-fire on monday and then it cut out! It would not re-start. There was a buzzing noise from a few componants under the bonnet (I last worked on a diesel engine way back in 2001 and they are all new to me), so I unplugged them systematically until I found all the "noisy" ones, and the car then started first turn of the key but ran very lumpy. Within half a mile the hesitation got much worse until it cut out again! Finally got it home and as it was late at night and snowing REALLY hard, it was left untouched for about a week! Next time I went to start it it took a few attempts and finally started reluctantly 4th attempt after about a minute of cranking. It was running VERY lumpy and would not rev at all. It was throwing out lots of white smoke which lessened as the engine started to warm. I tried revving the engine and it was very slow to rev but eventually increased speed and threw out a huge cloud of black smoke and soot. It hadn't been serviced for a while so I replaced the fuel and air filter. Also with it improving as it warmed up, I thought it could be a glow plug problem so I went to replace those too. I managed to replace the glow plug on cyls 1 and 2 but 3 and 4 are seized solid and I decided to leave them for another day! Now it won't start and I have ran the battery down trying. I have the battery on charge and will go out and try again in a few hours! Anyone come across a problem like this before? Any help and advice would be much appreciated.