So a few weeks ago i replaced the distributor in my 96 302 because the it was stalling and throwing a P0320 code. the new distributor fixed that, but now once the truck gets up to temp it will randomly start shuddering when holding a cruising speed. And its also throwing a Multiple Misfire code. here's the original thread: https://www.f150forum.com/f10/loss-codes-276936/
Personally I think that the new dizzy is bad, as I've made sure that the wires are separated and routed properly. Thanks

 

First thing to do is always the simplest. Recheck your base timing (pull spout connector) and verify that the timing is correct. A bad "new" part isn't unheard of though.

 

Could still be the wires, one way to rule them out is to get a spray bottle with a fine mist and spray water on the wires when it is dark enough to see any sparks (either at night or in a dark garage). If it's only happening once up to temp you may have better luck spraying it after a drive.

Could also be a failing ignition coil or like you thought a bad dist. Did you try retarding your timing to the factory recommended 10*? You can always advance it to where you have it but it may be worth a shot.

 

I can check the coil, its an Accel, but its only a year old. And i had the timing set at 16* prior to swapping the new distributor, but I set it back down to 10*

 

I've heard the 6ltr tune up is hard on coils, question though, once you reset the timing did you re-gap the plugs? May not be an issue but I thought that with the timing advance you also gap the plugs to a dif. spec, this could cause running issues.

 

So you're confident with the coil and distributor - does your truck have an ICM on the fender by the cruise control ? That's probably what I'd be looking for next.
Make sure you get the right color.

 

I have heard of problems where after the 6 litre tune up the hotter coil kills the distributor. I would check on that first. It seems as if something is heating up with the truck and then becomes faulty when its warmed up.