I have a 93 Prelude 4WS with the factory H23 engine in it. Originally my car would rev from about 1500 to 2500 rpm when the engine was cold. Once it reached about 150 degrees operating temperature, it would idle normally at about 750. I thought the problem was the idle air control valve and I bought a brand new one from a dealership. It didn't fix the problem. The next thing i did was "reassemble" the fast idle valve by stretching the spring on the inside and putting it back on. I also adjusted the idle screw located on the top of the throttle body. After playing with the fast idle valve and the idle screw, it stopped the revving. I was pretty convinced that maybe just the idle screw needed to be tightened because i tightened it right after i "reassembled" the fast idle and it immediately stopped. I recently changed my brakes on my own and it started revving at idle again but now it does it at full operating temperature. Any time i take it out of gear it will rev from between 1100 and 2100 rpm, even when rolling in neutral at 70 mph. I was thinking maybe a vacuum leak or something i did when i changed my breaks. Can anyone help me?

 

i had the same problem.... the fan sensor might be the case man... now since i have 4ws, i have other problems to worry about... finding another ball joint!