My honda has a surging idle?

I have a 1995 honda civic. It DOESNT stall or die when idling or coming to a stop, it simply surges from around 1500-2500. Now when the car is warmed up and i take off the intake pipe, i cover the bottom hole in the throttle body, and the surging stops but idle is still a little high. However, when I cover both of the holes in the throttle body, it idles perfectly. There is a lot of suction coming from the bottom hole. I already tried tightening the fast idle thermo valve (FITV) with no luck. And sometimes when I cover both holes and then take my hand away, it will idle fine until I shut the car off. There isnt a check engine light on. What could it be?
 
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