I turned up the idle timin on my 1990 civic dx and nowwhen running in park it changes high to low idle and back a few times... is it too high ?

Set the ignition timing, per the link below:

https://www.askmehelpdesk.com/cars-t...tml#post219963

If the problem persists, the Ignition Control Module (ICM) may be failing or there's an air leak (e.g. hose or Fast Idle Thermo Valve). To check the Fast Idle Thermo Valve, remove the cover (two hex head screws) and ensure the plastic ring, which goes around the valve, is rotated clockwise until it's fully seated--don't overtighten. If it's not seated, it allows in too much air, which the ECM keeps trying to adjust for. It's located under the IACV on the back of the plenum. It's hard to see, but it's there.