How old are the plugs/wires/cap/rotor?

 

Plugs, cap and rotor are only a few days old. (Swapped them all when I had the motor torn down). Wires are MSD 8.5mm Super Conductor and are a few months old (4-8 months old, not sure exactly how long though)

 

What brand plugs? What type? These trucks really don't like the rare-earth plugs..... (platinum, Iridium, et. al.)

 

I was originally running NGK Iridium, the plugs I just installed are Auto lite copper core 3923

Edit: These plugs were recommend by another user under a thread about the death flash, regarding using them with the hemifever tuner. I was planning on a tuner in the future so I decided to go ahead and make the plug switch now. Plus I have read that they are not fond of the big boy plugs either

This truck has 187k miles on it and it just came to mind that compression could also be a potential cause of the misfire and rev limiter issue. I have also noticed my fuel mileage started to decrease before I even replaced all these parts, and the CEL codes can also results of compression loss. Tomorrow morning I'll go pick up a compression tester kit and get back to yall with the results.

 

Done anything with the plenum yet?

If you have an air compressor, I would be more tempted to do a leak down test.

 

Yes, my plenum was blown so i used Hughes engines repair kit, felpro gaskets and plenty of rtv where required.
And I do have an air compressor so I can run the leak down as well.
Compression tests results still to come

 

Low compression cylinder 4
Tested cyl 2 dry: 155 psi
Tested cyl 4 dry: 105 psi
Tested cyl 4 wet: 130 psi

Didnt even bother testing the rest of them. Now it's time to figure out what to do. Thanks for all the input lads, much appreciated

 

Yeah, that's bad rings. You could try an engine treatment, and see if the rings aren't just stuck, or some such. Worth a shot anyway.

 

I'll give it a shot and see what happens. Otherwise, shes got 187k and 24 years on the clock, it's about time to pull the motor and rebuild it or swap it for something else anyway

 

408 build time?