A Ford focus does not have a diesel fuel filter. It runs on regular fuel. Preferably 87 octane
Dirty fuel filter will do that. Defective "kill" switch.
a dirty air filter or a dirty fuel filter will cause a diesel to smoke
Whenever it gets dirty.
Dirty fuel filter
Dirty fuel filter??
Probably a dirty fuel filter.
Poor flow of air into the vehicle. Replace the cabin filter every 30,000 miles.
Dirty air filter
Air filter dirty or bad injector
Dirty fuel filter, dirty injectors, for a start.
If the car has a turbo, the turbo could be shot. It could also be a dirty air filter, dirty fuel filter, or dirty fuel injectors. Another thing could be a fuel pump that is bad.
Fuel filter plugged?Air filter dirty?weak fuel Pump?