When i start it up in the morning or when the engines cold it revs up really high like its supposed to, id say around 2500-3000 for a little bit until the engine warms up. After the RPMs start to come down it will bounce around from 1000 to 2000 then after a little longer it will bounce around from 1000 to 1500. Seems like the IACV or something. After the engine's been running for a while it will idle normally but sometimes it will start to go up and down at a stoplight, but it only goes between 1000 and 1250. Its really driving me crazy! What could be wrong?

 

Mine sits at 2000-2200rpm every time I change gears try reving it to duplicate but no luck. But try this and see if it'll fix your problem. https://honda-tech.com/forums/honda-crx-ef-civic-1988-1991-3/how-fix-your-idleing-woes-fitv-iacv-2153910/

 

Check the FITV that sits underneath the tb. Take off the rear plate and screw the valve all the way back in. Check the tension on yout TB cable as well.

 

try a different iacv if you have one