Lincoln Continental stalls when talk foot off excellerator suddenly

What makes this 81 Continental stall. We drove it accross country but all the time mindful that it may stall. Somehow it always starts back up but not right away, you have to let it sit for 5 - 30 minutes. It seems to occur when you take your foot off the excellerator suddenly. If you decrease speed pulling your foot off slowly it doesn’t happen as much. It happens when you’re going fast or slow and everything in between. We have changed the fuel filter. Other known problems are oil leak and transmission leak. It runs strong otherwise.