2004 ford taurus 3.0 will not take take gas?

[Patricia]

i have a 2004 ford taurus 3.0 automatic when the motor is idiling i can push the gas pedal down the motor will rev up or take all the gas i want to give it but when i, m driving it i try to push the pedal down the motor will not take the gas or the motor goes powerless i,ve changed the mass air flow but no better