i have a 2008 focus cc and my engine malfunction warning keeps coming on when i sometimes start the car, it will turn off after i turn off and restart a few time but if i drive with it on the car feels sluggish. also sometimes when starting the car will rev like i have press the pedal to the floor or few times wont start at all unless i pump the pedal please can you advise me i am thinking it may be the acceleration sensor ? how much would this cost to repair ?