should a guy that hasn't worked on a car since the early 70's attemp to change plugs and a coil on 03 f150. 155k on orig plugs and code says #4 cly misfire

 

It's really not that big of a deal but I think it's worth the money to have someone change the plugs. As far as the #4 coil pack it's a easy thing to swap. One small bolt and unplug it and pull up and that's it....then reverse that procedure. I would go ahead and swap that cop out then address the plugs.

 

I have an '01 with 155k, I had a misfire on cyl 3 and bought a set of Motorcraft plugs, boots and a new coil for cyl 3. First two plugs were easy, number 3 was rusted into a ball of rust and snapped off as soon as I started to loosen it. Had to take it to local mechanic to have it drilled, tapped and a new insert put in. Mechanic said he would have had to do the same thing even if he tried to remove it. It was rusted solid. Number 4 looked to be a pretty tough plug to reach without the right extensions and universal joint. The 7 and 8 on the drivers side look worse, I don't see how you could pull those out without removing the fuel rail. If you are not comfortable find a good trustworthy mechanic and get them to do it. Make sure they use Motorcraft plugs, not some cheap plug. I was also told to replace the boots on any cylinder you are not replacing the COP on and crease them up good with dielectric grease.

 

I agree thats why I advised him to have the dealer/mechanic do the plugs. As far as the cop's they can all be removed without taking any fuel rails off. The OP pm'd me and told me that the cop was a breeze and he was letting the dealer handle the rest.

As far as your case....Pure neglect is what causes the symptoms you have.

 

All the other plugs were fine with no rust. Did the previous owner of my truck (I just bought it last month) neglect one plug by pouring salt water into the #3 COP? Seems odd that one plug would have this issue.

Here is #2 plug:


Here is #3 plug (or what came out in my wrench):


#2 seems fine for being in the truck 50K or more miles. #3 on the other hand looks a bit rough, not sure I would call it neglect. Seems like number 3 is in a spot likely to receive water from multiple sources (hood edge, A/C line right over it). Seems that Ford has had many years of plug issues in the 4.6/5.4 engines.