Fast idle thermo valve is the #1 suspect when the cold idle is out of spec. Since it happens to you when the engine has warmed up, focus shifts to the IACV (idle air control valve). To make sure it's the IACV you should first check your fast idle thermo and then make sure the idle adjusting screw is set properly. I've attatched the pages from the Helms manual for those procedures. If you still have the problem after doing both of these, it's most likely a bad IACV. Oh, and since this is a VTEC engine use the idle numbers that the Helms says for the B17A1. This is my '93 manual so that was the VTEC engine that year.