Intermittently dies out

I have a 91 voyager. The car has been in the family for years. It has been sitting for some time. It was put in storage about a year before. When it was driven before it would have the intermittent problem of dying out at low speeds. The lights would stay on and it could be started up right away. It usually happened when slowing down or going slower (less than 30 mph). Recently the minivan was given to me and I have been driving it. I have had it for the past month and it has died out twice like this. Both times I was pulling up to a stop sign and therefore was braking and I could start it right up both times. Any ideas on what to try first? This problem has really been a problem for a few years now but since the van is now mine I would like to fix it.