My girlfriend owns a 2008 Kia Optima LX with just a little over 80k miles and a 2.4L 4 cylinder engine. The problem started today when she was on her way to and from work and when I took it out to test drive it. For me the problem happened around 45 mph and her it happened at any speed. The car would accelerate as normal when you press down on the accelerator. But it would lose power as if you were moving your foot off the pedal. When you take your foot off and reapply pressure to the pedal it would accelerate as normal. I got it home and took out the air filter thinking it could be that. About 1.5 miles from my house it happened again with the air filter out. This time I kept my foot on the pedal and tapped it from the half position to the floor board a few times. When I did this it started to accelerate as normal after a few taps. When making my return trip it occurred in a parking lot while i was going 20 mph, but caught it self and returned to normal. Also for additional info she had the check engine light on for a year but it recently went away. I have no idea what code it was giving. Any information is much appreciated. Thank in advance.