1996 Ford Contour revving up and down problem?

96 Contour 2.0.
-Engine rev's up and down at idle or at a stop, with or without a/c on.

Mechanic thought egr valve but i clean it and same problem. What else can it be?
car has new timing belt and maf sensor.

Read more: 1996 Ford Contour revving up and down problem?