96 Acheiva- Runs to rich, stalling

I have a 96 acheiva that up until now has ran fine until yesterday. It was raining hard and the check engine light came on, I took it to autozone and they said the code was "engine to rich". Today, I start the car, drive a half a mile to the gas station to get gas and by the time i get there the check engine light turns off. I put better quality gas in it and a feul injector cleaner. It ran fine all day expet this after noon, when it started to stall at stop lights after idling, and the check engine light came back on.
and ideas?

Welcome to AF. Get the exact code and post back for help, also what engine.