I bought the truck used and it ran great for the first 3,000 miles. 2002 1500 quad cab 4.7L with 128,000 miles 2WD. although the engine compartment was just dusty-dirty I cleaned it with Engine Bright. It ran great for another 100 miles, then I got a check engine light and a misfire #1 code but I did not really notice anything rough I changed all the plugs and it ran better than before. Then the light came back on a week later and it ran rough, and got worse and worse until now it has a misfire code #1 & #6 and one cylinder is not firing at all. My first inclination would be change the coils and injectors but I don't want to just keep guessing and throwing money into it.

 

intermittent misfires on specific cylinders are usually electrical related.

There's so many variables its hard to know where to start. It could be the coils, so the first and best place to start would be to swap the coils from the 2 cylinders with the misfires, to 2 cylinders that have not logged any misfires. Clear all codes and drive it. If the light comes on again, read the codes. If the codes are the same cylinders, you have eliminated the coils as the problem. If they change to the cylinders you moved the coils to then you have confirmed the coils as the problem.

 

Welcome to the site, I agree with swapping coils and testing for voltage in the wiring harness for the coils