i have an 89 crx with a z6, obd1 conversion. a p28 chipped with crome...everything runs fine, no codes or anything. but the idle seems double what it should be. cold idle should be around 1500 going down to 600-700 as it warms up, but when cold it is at 3000 and goes down to 1500 as it gets warm. if i blip the throttle it drops down to half of the rpm and then shoots back up. for example, if it's still cold and idling at 3000 and i blip the throttle, it drops down to 1500 then catches itself and goes back to 3000. when warm it drops to ~700 and then goes back to 1500 if i blip the throttle like at a light or something.

i've messed with the IACV, i let the car warm up and unplugged it and it should have dropped rpms drastically, but it didnt. i thought maybe my 97 integra would have the same valve, looked at part numbers and they were the same, the two looked the same, so before i went out and bought a new IACV for $200 i tested the one from my integra that i know worked fine. but i had the same problem, didnt appear to make any difference in the crx.

i cut j1 on the ecu to go back to stock maps (nothing drastic done to the engine as of yet, just using stock fuel/ignition maps in crome) and it's giving the same problem and seems to have made it worse. now i get a surging idle. when i unplug the IACV it is steady though...

it seems like the ecu is telling it to idle differently, but if the IACV is disconnected, what kind of control over the engine speed does the ecu have? shouldnt it be none? haynes says the idle should drop to ~450 when the IACV is disconnected, but it is running the same speed for me. i tested the teg's IACV while it was in the teg and unplugged it while it was running and the car instantly died, but the same valve in the crx did nothing...

anyone have any ideas what this might be?

 

sounds like you may have a vacuum leak

 

Have you tried adjusting your throttle cable at the butterfly?