acceleration problem

Sometimes when I press down on the gas pedal after a couple seconds the rpms decrease as I keep a constant or increased pressure on the pedal. I have to take my foot of the pedal and press down on the gas again which inturn it happens again. if you have any suggestion I would appriciate it.

Dose the car surge when you floor it? Dose it run smoth when you are barly on the throttle? What Kind of car is this? When was the last time you changed your fuel filter? Check engine light on?
Need more information.