My 1998 Mercury villager van 6 cylinder 3.0eng keeps cutting off

My 1998 Mercury villager van keeps cutting off while driving it.
The check engine light was on so we took it to be put on the computer. The computer said it was the speed sensor and the knock sensor. We put the speed sensor on but the person couldn't get to the knock sensor. Could this be what's making it cut off? He changed the fuel filter it was stopped up some. the fuel pump comes on each time you turn the switch on. Some suggestions were a loose wire, fuel pump, a module, or a crank sensor. As long as the van is sitting still and just running it doesn't cut of . just when you are driving it cuts off. sometimes it will crank right back up and go sometimes it will crank back up and cut back off sometime it won't crank back up. it is turning over but just won't crank sometime unless you pump the gas. but it is fuel injected.