bought a vectra 2.0 TDi 1998, was driving down the road and a big puff of black smoke came out of the back of the car and then the car revved by itself, carried on revving even when the key was taken out.

What could this be? one mechanic has said turbo other has said Injectors. The turbo apparently was replaced before i bought the car

Heidi, November 2009

To much oil in the engine is the most common cause of this. Incompetent basic maintenance.
Very occasionaly a leaky diesel injector will dribble fuel which can run down into the sump, raising the oil level, but this should be obvious when you check the oil by the smell and look of it.
Drain the oil out and examine it to be on the safe side.

fred, November 2009

can also happen if engine oil level is too high!

k, November 2009

An oil leak from the turbocharger means that a diesel engine can run on its own oil...occasionally revving to destruction! Definitely a turbo fault.

John, November 2009