Had this problem on my TD4.----Due to partial corroded pins on plug and socket connection to the fuel high pressure sensor on left hand end of common fuel rail. Sprayed on some WD40 ,push plug in and out few times now runs well.First happened about year ago-repeated couple of times since but cured nasty problem very cheaply! See location Haynes manual page 4B 16. Possibly caused by engine cleaning pressure spray.