need help!! 1997 SL1

Alright long story short...My Check Engine light is on, after being reset several times..No one can seem to pinpoint the issue. My idol speed is roughly 1500 rpms, and OVERNIGHT it dropped to 400. It will instantly stall upon starting, unless the engine is revved for at least 20 min constantly. After warming up for an extended time, it will not stall. Any suggestions are highly apperciated! Thank you in advance :) :)

do you have the EXACT code(one letter, four numbers) that set the check engine light?