Going to give the history for past two weeks hoping this helps. 97 f150, 4.6, 265,000 miles, K&N air filter. Temp gauge was going a little high after start up so I changed thermostat and gasket, complete flush and fill of coolant system. It was about time for plugs so I took it to a mechanic and had plugs changed. ( Bosch Plugs) Truck ran fine on the way home. The next day it would not turnover, I pulled battery, took it to Advanced Auto and it checked fine. So I checked all connections, and finally changed starter. (in the rain, lots of rain.) It started and ran fine. The next morning after about a mile, it had a "dead skip". Went back to Advanced and they checked and said Misfire on Cylinder 7. (also EGR Flow) Checked plug wires, no help. Replaced #7 plug with an Autolite, ran fine for a week. Friday morning on the way to work it ran fine. That afternoon, skip was back. Checked wires again, replaced plug again in 7, (plug I took out looked fine, both times) still skipping. Back to Advance, Now a Misfire on 7 and 8.(still has EGR also, was planning on working on that this weekend) Idles fine, rev motor to about 3000 no skip, but when I start up hill, skip returns. Also checked for water in oil, in case of leaking head gasket, none. So coil packs, wires, plugs, injectors, not sure, where do I start? I could swap wires on 4 and 8 to see if problem follows. Or is that just me losing my mind over this.

 

one common problem is antifreeze leak at rear corner passenger side. might be the coil at that point. put it up front, and put the front in rear and see if you get a different code.

 

At the mileage you have, piece mealing a problem will take you a long time to get a handle on and make it appear some parts are a problem when they are not.
Replace the plug wires/boots, make sure you have no coolant/water leaks into the plug wells and the coil paks are good.
Some one is bound to reply that the BOSCH plugs are a problem but I keep defending against this because they never have positive proof beyond changing them and seemly the problem disappears.
You need to do the whole job and use good workmanship to solve the problems.
Good luck.

 

Thanks for the ideas. I did purchase a new set of wires and got #7 and #8 changed before it got dark. (#8 was bad for sure, broken) Problem gone running fine. I did notice some coolant around the top hose and neck. So I replaced the thermostat and gasket and checked hose just to be sure. As soon as I removed the thermostat the excees coolant filled the plug wells on 6,7,8. (no wonder those plugs are so hard to remove) Dried it all out and replaced the boots. Going to finish changing the wires this week. Thanks again for all the help.

 

Good to hear of the progress.