Classic/Antique Car Repair: 1985 cadillac, gm training center, computer functions

Question
since the battery was replaced the engine will not idle or respond to acceleration(surging at idle)

Answer
I remember 25 years ago or so attending a training course at a GM training center on the computer system that is in your car. The instructor warned us to make sure the ignition  key was in the off position when disconnecting or reconnecting the battery. If the key was in the on position the idles speed control motor can be damaged.You will need to check the computer functions to check this out.