I have a idle problem. my car idles at 2 grand until warmed up. Then once warm it idles at like a grand but like slowly surges betweeen a grand and 2 grand. I have the idle set screw down. so i know its not that. Im positive its not the MAP Sensor, or the IACV. What else could it be

 

Does your car have a fast idle thermo valve ?
Google fitv rebuild

 

do you have a CEL? or is it misfiring?

 

I had the same problem. The issue was I had bypassed my FITV(fast idle thermo valve) for some dumb reason. All I had to do was hook it back up and it was great. So if you didn't bypass yours, maybe its stuck

 

i had the same problem in my 93 ej1 b16a. im not exactly sure how similar the b18b is to my JDM B16a. Their is no other honda tuners in at least a 30 mile radius of where i live, well except for the occasional rice boy. so i have only experience with my engine. my idle kept jumping from 1 to 2 grand. they are supposed to idle high until the engine in warmed. but after that it should drop to normal.

on my car. when i would start it (cold) the idle would go directly to 2 grand and stay there for a few minutes. then it would be jumpy from 1900 to 1000. then from 1700 to 1000. and so on. those are not exact rpms. but as it would get warmer the idle would start to decrease but fluctuate as it went down. this problem started progressing. at first it would only do it sometimes. then it would happen everytime my car was started. after i drove it a couple miles it would stop. then it went to just fluctuating from 1 to 2 grand all the time. no matter cold or hot start. even when the clutch was pushed in. didnt matter.

first i cleaned my IACV thoroghly. removed it then sprayed carb cleaner in there until clear cleaner was coming out the other end. cleaned all my seals. put that back. then i took off my air intake and started the car. if you plug the 2 holes that are next to the throttle plate, on the left side of the throttle body that lead to the IAC Valve, with your fingers your idle should drop. if it doesnt your IACV is bad. next tried adjusting the throttle screw on the throttle body. still no luck. i then proceded to bleed my coolant system. air bubbles in your coolant system can cause a jumpy idle if your car has a FITV. I then took out the valve and took it apart. cleaned all of it with carb cleaner. cleaned the housing it went in. and put it back in. make sure the plate is bolted on before you start it. the more you tighten the fitv the lower it will make your idle. the more you loosen it the higher idle goes. since mine was to high i screwed it in about 2 full turns more than what it was. it was almost all the way out.

after that no more jumpy idle. if you tighten that to lower your idle make sure you readjust the throttle body idle screw. i also found a small vertical screw in the intake manifold that the throttle cable end connects to. i loosened this which loosed the throttle cable a bit and also lowered my idle. with everything clean and properly adjusted idle is fine. cold start idle around 2 for a few minutes and then drops slowly to around 800rpm.

heres a great how to on cleaning a FITV. it also shows how to take it completely off and clean it. but i didnt remove the intake manifold i just took off the cover where the valve is and pulled that FITV out and cleaned that and the houseing and put it back together.
https://honda-tech.com/forums/showth...e+thermo+valve

if none of these help try checking the gasket/gaskets on the intake manifold along with vacuum lines for leaks. i think i pretty much covered all the bases. but id say clean your FITV. Hope this helps man. good luck.