"check engine" light..not good

Hey guys, i have a 96 eclipse GS, and at 106k miles on the chassis (60K on factory crate engine) the check engine light suddenly lit up and my idle changed from 1k rpms to 1500-2k rpms, i assumed there was a vacuum leak so i bought a cold air intake (i was gonna do that anyway) and reset the car by disconnecting the battery for 1 minute, the check engine light went away, but when i took it out, it came back on, any suggestions on the problem?

The absolute first step is to get that code read and post what it is. There is no meaningfull help we can offer without that little bit of info. Poeple will attempt to take guesses at it, but they will be just that, guesses. Places like autozone and such offer free code scanning, hoping you'll buy the part from them. Or a friend with a datalogger can pull the codes for you.