i have a 1999 f250 with the 6.8L v10 with 129000 miles on it. i am having a really bad miss issue under load. It was coming up with a cyl 7 misfire code so i replaced the coil and that code went away not its coming up with a multiple cyl misfire code. ive been chasing this problem back and forth for almost 3 months if someone has any input it would be greatly appreciated. thanks

 

The things to check on that cylinder are:

1. Coil-the coil itself and the connector.
2. Boot-No cracks in the rubber and make sure the spring is not rusted.
3. Spark plug.
4. No water or debris in the hole.
5. Injector and the connector.

 

x2 with what JH says...i am thinking the same thing....

 

I had the same prob in my 99 V10! Except mine was leaking fuel out of the EXHAUST manifold at the same time!!! I spent more money replacing plugs, coils, and checked for leaks and everything else I finnally fixed mine. Still Not sure how, but I have a Hypertech Max Energy tuner and had mine programmed in the Medium setting, 87-89 octane. So, I reset it back to stock setting, and the wirdest thing happened. Its would crank and then just die.. I thought ah crap, so I put the battery charger on it for an hour and it started right up, but still had the same problem.. So I retuned it to the Premium setting, same thing happened. Cranked over a few times and died.. So iput the charger on it, the battery would never charge up all the way, so I checked the Positive cable to the battery, and it was loose, so I tightned it and the truck fired right up and no mis, no leaking fuel from the Exhaust.. So, I dont know if it was the program that fixed my promblem, or the fact that my positive cable was loose and I took it off to let the computer reset and retightened it. but heck, Take your positive cable off the battery,make sure its clean and not broken and hook it back up. Then get in and turn the key to the "run" position but dont start it. let it set for about 30 secs and try it.. You have tried everything else...
Just an Idea... I know mine was doing the same thing..... and it fixed it..... I dunno, no-one else had any idea!