1991 Plymouth Grand Voyager 3.3

Runs fine80% of the time. Always starts up and accelerates. Except at times it will die when you put in gear take your foot off brake still runs fine until you touch the accellerater again. Then it dies. It will start back up and revs in gear or with foot on brake take foot off it dies. Sometimes 20 times sometimes just one. Then may not do it again for 2 months but always eventually works eventually Please help been towed and started and ran as soon as it gets home.
Thank You in adavance, Ben