Need help ..Hunting Idling

Hi guys, I’m having this idling that goes from (500 - 1000 rpm) when the engine is about warming up, temperature guage at about 1/4 up. It stays pretty stable when the engine is warmed up though. I’ve searched the forum for solutions to the problem and I’ve done almost all the solutions stated. These are all the things I’ve done so far:

-cleaned and checked IACV
-replaced fuel filter
-replaced timing belt and checked timing
-replace FIV…$80!!
-bled coolant
-checked vacuum hoses
-replace PCV valve
-cleaned air filter

I’m also thinking of replacing the TB and intake gasket as well as all the vacuum hoses just to be sure I’m not having a vacuum leak somewhere. Currently running at about 18 inHg when at operating temperature which is kinda at the low end of the specs. Can anybody please tell me if I’m missing something here, any suggestion is greatly apperciated. Thanks.

k, i had this exact same problem w/ my prelude, and finally tracked it down. first of all, the thing that is causing this is a vaccum leak somewhere after the throttle body. first thing i’d check is your TB gasket, then be sure the 4 nuts holding it on are torqued to spec. if this doesn’t work & there are no vaccum leaks, you need to replace your fast idle air control valve. people tell you to check your iacv, but in reality there are 3 valves that control your idle. the one i’m talking about is bolted to the underside of the throttle body. the best way to check it, is once the car’s warmed up, pull your air intake tube off the throttle body. w. the engine running, put your finger over the lower hole before the butterfly (you’ll see what i’m talking about) if it’s sucking alot of air, you need to replace this valve.

Thanks for the reply. I know exactly what you’re talking about. You might have missed the things I’ve done in the previous post or I might have edited it after you’ve read it. Anyway, I replaced the Fast idle thermo valve yesterday (bought it from Acura for $80…!). But the interesting thing is that its still sucking air even after the radiator fan came on and off. Tried covering the hole in the TB but it does not affact the vacuum reading. I don’t know if that is a defective “new” part or that is the way it should be, just drawing a little bit of air at operating temperature. Do you think I should replace the gaskets and clean the TB in the process in any case? Or is there anything else that I can do? Thanks.