Car stalls

I have a 1988 Chevrolet celebrity with 56000 orig miles(stop and go trafic mostly) with a 2.8 mfi engine. sometimes it stalls when coming to a stop and sometimes when I start it back up it races for a few seconds. someone said if I had the battery disconnected to long it doesn't run right. the car has been ran just idleing a lot because I am working on the ac so I have been turning it on and off a lot, to to get it going I have press the gas pedle a little, it also races at that point but always returns to a good idle. do i have to do anything special for the computer to work propery after the battery is disconnected for a while? I have had this problem before for the same reason and it seems to get better after driving it for a while, I am curious about what is actually going on with the computer after it has no power for a while? If anyone could help i would appricate it.