Dies when at idle

I currently have a 2002 mitsu montero sport, v6, 4 wheel drive, auto trans. My problem is that after my battery gets disconneced (for any reason)and then reconnected, ill go back to driving my car and come to a stoplight. At the point where I need to start slowing down to a stop, my car idles down very low and dies unless I get moving again. Im not sure if the battery has anyting at all to do with this, it very well might be a strange coincidence but the idleling is the problem. It has done this two previous times and once it went away on its own while the other time my husband cleaned out some kind of valve that was connected to the idle throttle(?). The car needs a tune up in the worst way but could that be causing the strange dying episodes? Thank you.