My Bronco is 1985 Drive Train 1979 351w bored camed and blue printed, body is 1988 changed after i rolled it.
Problem: Gased up truck drove 40 miles and stopped to use restroom and get a drink. tried to start truck and it would act like it was firing but would not run. got a jump after i ran the battery low and i started it from under the hood. It was running very rough until i give it more trottle then it will run smooth from 1500 to 2000 anything over that it is running with a top speed of around 55 and it sounds like it is running on about 5 cyliders. when it dies at an idle the tach. seems to just drop out like all power was lost. i have always had some troubles starting the truck from inside during really cold weather. Almost like the voltage draw is killing my spark, or the switch is faulty. i can normally start it under the hood with no problems. i can only keep the truck running now if the idle is around 1200 anything below it will run fine for a few minutes then it starts the rough and dies. When it dies it is very difficult to get to fire back up. i want to beleive it is a module or something but i'm not really sure what to check. Any help would be great. I do wrench on vehicles quite a bit but not much on fords.
The Ignition system is all the original 1985 351w 4brl. Thanks

 

Welcome to FTE and the Big Bronco Forum. We will do our best to get you the most accurate info we can.

1985 was Duraspark II maybe? If I am recalling correctly. Ignition is controlled by a small grey/gold module with a couple/three ROUND connectors coming out of it. They are known to fail either partially or just up and DIE and leave you stranded. Unfortunately, the only fix is to replace it either way. There is also an inductive trigger and excitor ring inside the distributor UNDER the rotor. (Think of it as a set of points without the physical contact). The early triggers were not as hardy as later units and if they fail the module has no idea when to fire the plugs. I'm certain there are folks here who can help you troubleshoot this better than I can but if the problem occurred that suddenly, I'd be leaning towards a failed/failing module.