Hey everyone I have a 88 CRX with a 91 b18a1 under the hood when my friend showed still drove his teg his idle surged but only when it was cold, few months later he wrecked it I got the engine. So when I swapped it over it did the same thing only surged while cold however today I decided to clean the intake with 3M Intake plate cleaner. After I cleaned the throttle body fired the car up same surging idle because it was cold but when it warmed up fully it was still surging faster than it ever did before from 1k to 2k. I swapped out the fast idle valve and IACV for known good ones. Then my idle calmed down a bit still surging every now then and when it isn't surging its sitting pretty at 1400rpm wtf is going on...?

 

Maybe you should adjust your base idle?