check cap and rotor..... check valve clearance "cold"
You have connected the wires to the wrong plugs.
It is feeling silly and my other answer is it is behaving badly
vacum leak
check the coil pack
The most likely cause of a 1992 Ford Aerostar stalling while idling is bad spark plugs. The plugs should be changed and the timing checked to resolve the problem.
Coil pack on one of your spark plugs may need to be changed. Have OBD II scan done to determine which one.
Fuel injector?, wire? manifold leak?
Bad plug or something is misassembled.
have you recently changed the timing belt? or maybe it's off a tooth.
Bad plugs/coil/wiring
It is probably your spark plugs misfiring.
Check spark plugs, plug wires, do a compression test