My car will sputter and start to slow down if I've driven on the freeway more than 15-20 minutes. If I try and give it gas, it just seems to decelerate quicker. Pumping the gas seems to get it back up to speed, but it will continue to sputter regardless, and will stall if I stop. Stopping and turning off the car seems to help, but the problem starts again, but sooner. We've had a tune-up and **replaced the fuel filter**. I have no idea what this could be.
Losing Acceleration After driving on the freeway on 1991 Plymouth Acclaim
sounds like you have a fuel pump starting to go bad, to really know you will have to hok up a fuel pressure gauge and drive the car until the problem happens and read fuel pressure at that time , depending on the engine you have .. 4 cyl shoould have about13 psi ,, 6 cyl. you should have 38 - 40 psi
i would check the fuel filter when was the last time you had that service