Idling Problems, PLEASE HELP!!!!

I have a 1991 Acura Integra with a 5 speed non-vtec engine.
I have been having idling problems where starting up the idle is high then when i start driving and stop the idling is still high and starts to fluctuate from about 800 RPM’s to 1700 RPM’s. It seems that when i turn on the AC the idling problem stops but still stays higher, like about 1100 RPM’s, but if I leave on the AC in about 20 seconds the RPM’s start climbing and then will do the RPM fluctuate just like when i left it off. I dont know what to do, I have tried to check the IAC Valve and it clicks if voltage is applied, the ohms are about 12.3, which is supposed to be normal and there is plenty of voltage when the plug is tested. Could cleaning the IACV be the problem, if so how do i clean it and if this couldnt be the problem then what could it be. I heard it could possible be the ECU computer. PLEASE ANYBODY HELP ME!!!
I’m trying to sell the car but want to fix the problem before I sell it.