check the wiring to the coil. not just at the plug, but all the way down into the loom on top of the tranny. fought this with a friends, replaced the coil wiring pigtail ($14 through ford) and still couldnt get the thing to act right or start all the time, or even stay running. ended up the wiring for the coil pigtail was messed up further down in the loom by about 5" than we had spliced.
first check your voltage at the plug and jiggle the wiring around to see if there is anything. if you don;t have voltage check the usual culprits first,,, fuses, etc. then start hunting down wiring.