idle problems. sputtering, barely running.
i had the truck jacked up a few hours ago checking out the front end. i lowered it back onto the ground and went to start it to back it into a parking spot. i started it up, and the idle went up to about 1200 like it always does and began to come back down. it dropped below 500 and the truck began to sputter and barely run. battery gauge was going crazy, but thats probably because the alternator was providing power and then not, because of the sputtering. i gave it a few revs and eventually it went back to normal. i drove it around and it drove fine. i parked it and it sat for about 20 minutes. i was curious to see if it would do it again so i went back out and started it again, same thing happened. i shut it down and it sat for another half hour. i did a little reading in the haynes manual and went back out to check it again. i started the truck and it ran perfectly fine, as if nothing was wrong. its got a check engine light, no idea what its for though. i've done some searching on here and here's what i've come up with to check
idle air control
intake manifold gaskets
anything else that these symptoms point to that i should be aware of? i was hoping to get through winter without doing the gaskets, but i guess i could go outside and freeze my fingers off and take care of it.
understand that i know my way around cars pretty well. i'm just hoping someone has had these exact problems so that i don't go sinking more money i don't have into parts that won't fix the problem. thanks in advance.