I have recently bought a 307 HDI Diesel and over the last few weeks I keep getting the message 'unlbock diesel filter'. My husband had undone cap as noted in Haynes manual and drained out water, on a number of occassions. The last time was Saturday night - the car hadn't been driven and the same message came up within 2 miles the next day I drove it. It also seems to suddenly pull back and won't accelerate then suddenly gets a burst of energy. Can anyone give me any advice?