I have a 2003 Elantra and it is having trouble climbing hills. Also, When I'm in gear, if I push the gas pedal to much it revvs up the engine and pretty much loses power. So, I have to keep it at a certain speed just to keep it going. I looked down at the front right wheel because I suspected the speed sensor. I also had the engine code read and it said speed sensor is bad. I replaced it, but after about 50 miles it started doing the revving thing again, but not as bad.