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.

It could be an idle air control valve that is faulty or needs cleaning if the issue is only at idle and you have no other driveability problems.

Other culprits may be an O2 sensor, corroded wiring, or a dirty throttle body that is not able to take in sufficient air with the throttle plate nearly closed.

It's the IACs job to control the Idle. But if there's a VACUUM LEAK it can't do it's job. Check your Vacuum, it should be high and steady. Or just look at all your vacuum lines and fittings. Other suspects are the Throttle Body and Intake Manifold Gaskets.

One of the rubber elbows on the PCV hard lines has rotted through and you have a vacuum leak, a very common problem. The twin cam Contour had the valve way at the back adjacent to the firewall - pia.