here is the problem, first start in the morning, the engine revs up to 1500 - 1800 rpm, which is normal i believe. However, it won't idle down to normal range (650-750rpm) . (even if i drive the car for a little while). it revs right back to 1500 rpm as soon as i push the clutch in. BUT if i warm the car up for 4-5 mins/drive it for short distance until the engine/coolant reaches the normal operating temp, THEN turn the engine off, AND restart it again. it idles perfect. I cleaned the IACV and TB with carb cleaner a week ago and it didn't fix the problem. any1 has any idea why? Bad IACV? Bad ECU? Sensor? or something else.
appreciate for any input.

 

So many threads about idle problems recently!
Double check your IACV, check for vacuum leaks, if you have a FITV my guess would be that is the problem.

 

^^^ what he said. check out the fitv if you have one. heres a link on how to fix it. https://honda-tech.com/zerothread?id=699787

 

vacuum leaks checked, found, and fixed.
my car doesn't equip with FITV (2000 civic SI)
i guess the IACV or the ECU do the job
I wanted to replace the IACV, but backed out after hearing so so many ppl said replacing the IACV didn't fix the idle problem.
anymore idea?

 

I've got the exact same problem with my B18c swap where it will only idle well after I warm it up then shut it off. I've cleaned IACV, checked vac leaks, etc. but haven't figured it out. by the way are you running skunk2 manifold and/or hondata gasket?

 

mine seem to idle that high on cold starts (jdm b16a) but i feel its normal..once it wamr sup in a few minutes it remains at its 750-900 idle

 

no, i am not running skunk2 manifold and/or hondata gasket
but i do have an aftermarket aem intake and catback which i don't think it would cause the problem.
cheehee, did you replace the IACV???

 

I also took her to a honda dealer b4 and they found nothing wrong as USUAL

 

I have not replaced my IACV, just cleaned it. After cleaning, it did effect my warm idle for the better. I'm going to bleed my coolant again because it may be air bubbles causing the problem.

I asked about skunk2 and gasket because I thought it may be a grounding issue for the manifold sensors. I wired a couple grounds but it didn't change anything.

From what others have said the IACV and MAP sensors are the root of most idle problems so I'm going to test the wires for continuity to the ECU as well as voltage readings. I also have a chipped p28 that I'm going to try and see if it changes anything.

Beside my cold idle problem I also have a rolling idle issue where it will jump about 1500rpm until the car stops then it drops back down.

 

Get a new throttle body gasket while you're in there. It doesn't take much of a hole to ruin your idle characteristics.

 

speaking of throttlebody gaskets....is the type r one different from the GSR gasket other than the diameter? I got my tb bored out to match ITR specs so I had to use a new ITR gasket. I think I matched them up and saw no difference but can't remember for sure.