Idle surging in a ’92 Toyota Celica GT

Check for holes or cracks in the black plastic pipe between the air filter and the throttle body.

Check the distributor cap and rotor, check ignition timing, check base idle speed.

Disconnect and plug the vacuum hose to the EGR valve and see if the surging goes away. If it does, check EGR operation.

============= Try spraying some TriFlow into the rectangular opening for the idle air intake valve at the bottom of the throttle body right in front. Seomtimes the rotating drum inside the valve sticks and the teflon in the TriFlow seems to work best in freeing it.