Ford Focus 1.8 TDCi 115 bhp 2003 model starting problem?

Twice car has problem with starting after short journey in the wet. At first did not realise that the car had started as it was idling at about 500 rpm but no response from accelaretor pedal, Almost as if cable had broken but no cable on the car. Sorted it self out in a cloud of black smoke after about 30 mins