Within the past month or so my car was having problems accelerating up hills. I would press the gas pedal down completely and still the car seemed to struggle up an inclines - however, it always eventually speed up. And it accelerated just fine on flat ground. The last time I used the car I had been driving up a hill when suddenly the car begin to make a different sort of noise, pressing the gas pedal produced a deeper louder sound. And it kept at the slow speed up the hill, but was unable to accelerate. On flat ground revving the engine produced the same sound.