Ford Fiesta car is loosing power when pedal is pressed . black smoke coming out of exaughst any ideas what it is

check air filter, breather pipes, also check if plugs are all sooted up?? try some redex into the fuel tank itl clean the fuel system as you drive it.

It's a diesel .Possible causes of black smoke .


Black Smoke
This is due to a air to fuel ratio imbalance, either the fuel system is delivering too much fuel into the engine or there is not enough clean air (oxygen ) a few things to look for :

Faulty injectors (injectors need attention at about 100.000 to 120 000 miles)
Faulty injector pump
Dirty air cleaner
Turbocharger or intercooler faulty
Problems within cylinder head, valves clogged up due to faulty EGR (exhaust gas recycling unit)
White Smoke

took car in garage for injector problem came out worse than when it went in .it only passed its mot two weeks ago dont think it would pass now. so annoyed payed a lot of money an car seems undivable. thanks for info