Need a little help. My nephew has a 1998 F150 with a 4.6L Triton. He had the code PO308 - misfire on #8 cylinder. He has changed all the spark plugs but still has a bad miss. I tried swaping the #8 spark plug wire with another wire and it still came up the same code. We kinda rulled out it was the plug wire. We switched the coils to see if the it would come up with a different code. Drove the truck - still had the miss but did not set any codes. My nephew said he would drive it around tomorrow and see if the check engine light comes on. I'll recheck it then to see if it comes up with a different code.

Is there any common problems with this type of engine? Can the coils be checked and what would the resistance specs be?