1997 Mazda Protege Reset Check engine light, now not idling

My Mazda had a check engine light on, couldn't find anything wrong with it, so it was reset by removing the negative side of the battery and holding the brake for 30 seconds. Now when I start the car initially, it won't idle properly. It goes almost to zero and almost stalls out and then goes up to about 800 RPM. Do you know what could be done to fix this idling problem?