Hey everyone. I have a 1982 F-250 that i have slowly been resurecting over the past year. it has a 351W,c-6. Ive since put in a new rebuilt 351, just had the c6 Rebuilt. It also has hooker pro comp headers, Edelbrock performer intake and a Holley 600CFM 4bbl. Now for the problem. I have been having one problem after another with this truck. It ran like crap about 2 months ago and i had the stock intake replaced cause the EGR valve was acting up. Then the carburetor went and put a new one in. The truck went fine for about a week after that. Then all of a sudden on a warmer day it was probably 65 ish and early spring i was going down the road and the truck started bucking. but it didnt do it constantly its on and off. If i look at my tach it goes way up to 3-4k rpm and drops back down to normal when it bucks. I thought it was my tranny going so i had it rebuilt :/ waste of 1grand right there. But now its still doing it. I tested the ignition system and its not getting a constant spark. ive replaced the ignition module it still does it. Ive replaced the coil as of today and its still misfiring. It seems to only do it on hot days and when the engine gets warm. I will be driving down the road and it starts bucking and it goes between running on 8 down to almost 4 cylinders then back up to 8. and when the engine gets warm it wont hold an idle and it jumps around rpm wise if i keep my foot on the gas to keep it running. I have tryed to describe this as best as possible and need any help i can get. Its a duraspark II system. I am running out of ideas on what the hell is going on. Please help Thanks

 

I would replace the plug wires, make sure they are routed properly and in the right firing order. you may also have a bad dizzy. What plugs are you running.
You might put some heat covers over the wires down by the headers to help protect them. If you pop the hood at night with the motor running you will see if the wires are arching at all?

good luck

 

I'd have to agree. The setup you have is pretty simple. I had a similar problem and it ended up being my carb, but you've already replaced that. Coil's good, ig mod is good, hot wires are hot when they need to be, and grounds are good. Ain't much left to check but the dizzy, plugs, and wires.

 

I popped the hood at night and no arching at all. The weirdest thing is it only acts up on warm days 60+ and when the truck is warm(driving around for 20 minutes or more). Ive stumped the local shops with what is wrong and as i said before i replaced the iggy mod and coil and the distributor looks fine. The rotor is clean and the contacts are fine also. I just cant figure it out. And its so random when it does it and it only does it on and off every few minutes when the truck is warm. Its hard to explain and i wish i could get a video to show what its doing.

 

Maybe your fuel pump is going out? this almost sounds like maybe your altinator is failing maybe causing the motor to run on the battery juice which after awhile will cause similar issues. I would drive it get everything nice and warm then take the alt into a parts house and they can test it.. a cracked cap will also cause this, an might not show up until it gets warm to.

good luck

 

It certainly sound electrical, seeing as how it gets warm, craps out, then stops. Almost seems like a short somewhere. Like somethings getting warm, it expands enough to release the ehat (and cause your problem), then cools down and contracts again, then heats up, etc.

 

Thats why im thinking dizzy cap. what kind of plug wires you using and type of plug itself?