94 Tercel DX revving problems when light pressure is applied to gas pedal.

When I put light pressure on the gas pedal, the engine revs up and down, and cause the car to jerk somewhat because of this. Though, when I am accelerating faster, and am putting more pressure on the pedal, I don't have this problem. This mostly occurs when I'm just driving in residential areas and keeping up my constant speed, therefore only putting light pressure on the pedal every so often. The same happens if I am just parked and slightly pressing the gas, the engine will rev up, then down, up then down, ect, until I press it harder.