hi have a 84 bronco 5.8ho has a miss in #5 i cant get out comp. is 130 lbs new cap wires-rotor-coil-plugs still have a miss after it runs a few min dosent seem to be there when its cold really tell it when it starts to warm up any ideas were to go next would really hlp tks

 

The only thing that controls spark timing in these rigs is the DS-II module and while its unlikely and extremely uncommon, it is possible that the module is misfiring the number 5 position. Be aware though that this is NOT a typical failure for a Duraspark module. (They usually just quit without ANY warning resulting in a complete "no-run" situation). Duraspark modules can get "eccentric" under extreme thermal changes so again, while its a long-shot, anything is possible. Given that everything else in the ignition system seems to be either new or recently replaced, there isn't anything else (electrically) to look at.

Is there anything to indicate that you might have a sticky valve? Can you get consistent compression readings with repeated operations of the piston? Perhaps a stem seizing in a guide at operating temperatures or above a certain RPM.

 

i did pull the valve cover and watch the valves work and they seam to be doing fine i did discover that if u pull the choke part the way closed it seams to start firing on all 8. when clod start up it fires on all 8 till the choke starts to open then looses #5

 

Have you tried replacing the one plug again? It may have been dropped. Also, a former Ford shop foreman likes NGK. They had some problems with carbon tracking with Motorcraft. The V-groove works good for me.

I don't know if the firing order on the 84 is the same as my 94 where #6 then #5 fire sequentially. I have 6 & 5 wires separated in the loom to prevent cross firing.

 

replaced the intake gasket and carb gaskets still have same problem #5 dead at idle and miss driving, can the carb be causing this? its a holly 4180 stock carb truck has 123k miles on it thanks

 

Have tried switching plugs and wires around to see if the miss moves

 

moved plugs and wires still #5 is down when choke is on its seems to be firing until it starts to open the more it opens the worse it gets till it becomes a complete dead miss

 

ok got the miss fixed. it was the carb; put a new rebuilt one on it and it cleared up runs perfect got the carb from Carburetors Exchange{800-491-2633} for $200 put on run perfect had to make no adjustments. thanks for all your help

 

Glad u got fixed even happier that you posted results mabey it will help someone else out