got a ford cmax zetec 15000 miles on clock problem started a few days ago when i excellerate there seems to be a loss of power (juddering) this only happens when the car is cold once the car has warmed up it seems fine.i must admit i have allowed the car to run low on fuel a few times any ideas what the problem could be

I'd start with checking the engine coolant temperature sensor in that this will extend the injector pulse time when the engine is cold