I've replaced plugs, wires, and crank position sensor, and also swapped my coils from side to side and the miss stays in cyl #8. Any other ideas? All I can think of is perhaps an injector issue.

Truck is a '97 F150 4x4, 4.6L automatic with 16x,000 miles on it.

 

Try swapping the injector, if thats not it could be internal. Do you feel a miss? If you don't feel it then your PCM could be the problem.

 

UPDATE:
After posting this thread, the misfire has moved to cylinder #3. I replaced the coil pack with one that is known to be good, yet the misfire persists in its new home. Later today after the engine cools I am going to pull the plug and take a look, and if it looks good add a healthy dosage of dielectric compound and put it all back together. Any other ideas? What could cause the seemingly random misfires?

 

I wouldn't mess around with it - plugs, wires, two fresh coil packs or you'll be pulling your hair out - get em from Global auto and pay half price..

You need to get your motors integrity back ...

 

All of that stuff is essentially new, and it's all motorcraft parts, yet the misfire won't go away. I'm already beyond pulling my hair out...

 

I know how that is. Looks like all you have left to replace is one coil correct?

What cylinders is the known good coil handling?

How did you determine #8 was misfiring?

How old are both coils?

Did you have any water at all on the motor or did you wash it recently? Are all wires sealed w/wire sealer?

Do you see any spark/arce in the dark while your motor is running.

If your running a stock coil by chance that's over 6 years old - it has served you well and needs to be replaced..

How old are the wires and plug exactly ?