I have a 93 f-150, with a 5.0, auto 4x4. Anyways it one of my plow trucks, and the driver said it was missing especially when he would go in to the pile of snow, like under alttle labor. Told him to bring it up and I would check the plugs etc. He said it would'nt do it all the time, but after running it for say 10 miles or so. I put new plugs, coil, wires and a fuel filter in hoping it would cure it, took it for a spin and ran great for awhile, then started missing, took it home and put some dry gas in it and let it set. I then drove for probably 80 miles and ran grat again, stopped at a store, was in there for 45 mins to an hour, came out started it up and it started missing. I noticed there was about 3/8 of a tank of fuel, in the front tank, so I went 2 blocks and fueled up. Left there and it missed for 4 miles, then ran pretty good for about 20 miles then started missing again.
When its missing its like running on 8, then 5, then 8, then 6 etc.
I'm heading out today to get a code reader.
Any Ideas??

 

I got a code reader, and code 34 came up, which is EGR valve position (EVP) sensor, or pressure feedback EGR (PFE) sensor: signal voltage out of Self-Test Specification limits, or signal voltage above closed limit during normal engine run operation, Or Signal indicates insufficient EGR flow.
I replace the sensor, took it for a spin, started missing right off the bat, then cleared up. I'm wondering if the last possible thing (signal indicates insufficient EGR flow) means the EGR valve itself is plugged up. If it is how does a guy go about cleaning it out, or do you replace it also. Thanks in advance.