I have a 1986 bronco 302, ( new truck to me) . When i accelerate it starts bucking ( missing) if i push it passed 2000rpm when driving it gets worse. Can usually get about 45mph with only occasionally miss anything passed that gets worse. Last night at 45mph i put air on and it got worse, turned air off and ran headlights and it got worse again. I have changed coil, dist, cap rotor plugs,wires, ignition, fuel filter. Idles fine, revs fine, . Tac needle drops everytime it bucks.alt is charging at 14.4 volts. Do those engines have serpentine belts or v belts, mine has v belts, and 2 belts off alt. I thought is voltage regulator bad inside alt? Help? Thanks

 

Your TFI module and stator may be failing or the ignition coil
Use a spark tester on the coil wire and watch the spark
Use another spark tester on a plug wire just in case
See if the spark goes away when the miss happens
You can use two coil wires and run the tester outside the hood and drive it if necessary for testing
Use both types, The type where the spark jumps the gap and the ones with the light
Watch the one while you listen for the other

 

I would fuel pump to the above list as well.......