I'm getting codes for misfires on cylinders 2, 3, 5, and 8, and P1300 random misfires. Since those cylinders are all on the same coil, I suspect that coil, or the wiring to the coil. Those cylinders are on both banks of the engine, so it would seem not to be vacuum leaks, O2 sensors, cats, or other causes.

Do these things usually fail on a single side, or both packs at the same time? Is my diagnosis sound? How do I test for it?

Thanks,
Keen

 

That does sound like a bad coil or wiring, like you said. Are there fuses for each coil? I don't know. I guess it wouldn't hurt to check. If not, you could try swapping them and see if the misfires follow. That's not a fun job though. There's not much room back there.
Does the truck run at all? Or are they intermittent misfires?

 

Thanks for the reply. As it turns out it was my own fault. I just finished up a head gasket job, and apparently I didn't get the right side wiring harness connector fully seated when I put the coils back in. Running fine now, except for an annoying ticking from the left bank. I guess I should have ponied up the money for new lifters when I had the thing apart.

Keen

 

That'll do it.

 

Best possible outcome!

 

That's great that you found it and it didn't cost you anything, aside from a little stress! We all make mistakes like that from time to time. Especially on such a big job.