car has trouble starting, what could it be? Options

[6strngs]

yeah, I've pretty much noticed this since a little before I got the car, but when I go to start it up after it's been sitting a few hours, it'll start, and the RPMs will shoot up to where they are supposed to, but when they come back down, they don't stop at 750 or whatever idle is and keep dropping until they reach zero and the car dies... so I'll start it back up, and in order to keep the RPMs up, I'll rev the engine. but as soon as I let go of the gas they drop real low again, so I rev again. usually, once I rev it to ~6000 and let it come back down it'll idle fine and then run fine for the rest of my trip, and if I shut it off for a while and come back, it'll be fine. but if it sits for 6 hours-ish or more before I start it up again it'll do it again...

what could be causing this?

[6strngs]

alright, I'm gonna see what I can learn tomorrow. tonight, after playing some more, I took a small hose off of one thing on my throttle body, and it made my idle jump to about 1,800 rpms. So I drove my 5 miles to work like that, and then after work, I went back to my car, at this point it's been sitting for about 6 hours, and it's 11 o' clock and pretty cold outside, so I figure it would do the start and then die thing on me, but because I had removed that hose it didn't die on me. and after a good long search through my hayne's manual, I see something about an ISCV (idle speed control valve), now, when I was looking for this last time, I didn't find anything because I was looking for an IACV (idle air control valve) anyway, after reading though it, I think that what I cleaned before was not my ISCV, so I'm gonna rip my throttle body off again tomorrow and see if I can clean my actual ISCV and see if that fixes my problem... though I am still concerned about my PCV putting oil into my intake, and I'm wondering if that is what might've caused my ISCV to become overly dirty in the first place... anyone know more about any of this?