i have a 90 CRX DX with 1.5 DPI
and sometimes for no reason my idle will jump
up to 2200 rpm's if i tap gas pedal sometimes it will drop to normal.
sometimes it won't
it does this out of the blue and will only do it for a wile
usually stops after an hour of driving or so.

 

anyone know whats causing this

 

Check for loose or corroded wires all along your harness, especially around the throttle body and the front driver side where your AC condenser (?) is located (lower right hand side when facing ftont of vehicle) I had a bad wire there and any time it touched it told the car the pump was running so it jumped rpms to fuel the extra drain on alternator.

Justa guess, but it could be any number of things