92 Escort Accelerates without pedal depression

Hi. My 92 Escort LX has recently begun accerating on its own. Often, (but not always) when i depress the clutch or put the car in neutral the engine revs extremely fast to the point of having to turn the car off. When driving down the road in gear at times it accelerates on its own. This doesn't always happen, although it seems to happen more frequently after a quick acceleration. Sometimes what fixes it temporarily is putting in the clutch and quickly reving the engine high, which afterwards sometimes brings it down to a normal RPM.

Any thoughts?