1993 Golf - basic model 4 cyl not GTI/V6 etc.

The car has an intermittent fault where it cuts out completely - we've tried replacing fuel pump and distributor. Fuel is getting to the injector, the plugs are sparking.

It cut out today when the car hit a bump but this is not the regular cause. After it has cut out, when you try to start the car - the engine doe not fire and when you stop turning the engine over it seems to run backwards for a couple of revolutions and there is a little puff of smoke out of the fuel injector. Otherwise it runs very smoothly.