Hi I have a 96 f-250 W/351 w and I can start it first thing in the morning and seems to run fine for a few minutes but after running about 2-3 min it starts missing on the #3 cylinder. I pulled the #3 plug out and it is like brand new and dry .the plug is firing but don't seem to be getting any fuel . The fuel rail is clean and I put all new fuel injectors in, I put a new computer in it, also I put a new map sensor in. I'm stumped .any information? I pulled the plentum off and used a test light on the injectors and they all light up.

 

Wiring issues is all that's left. You replaced everything .Part guessing gets expensive, doesn't it?

 

If you are up to it,

It's not easy, but there is a way to determine just which is the problem.

First you switch the plug with a different cylinder. Then switch the injector with another different cyl

If the problem is still with #3 cyl , you have ruled out 2 things.

If the problem has move to a different cyl , depending on which one you switched injectors with and which one you switched 2 plugs with. Just do not use the same cyl to put the parts from #3 in.
As I said it won't be easy , but if you don't have the equip to do detailed testing that is one way to help isolate the problem.
If you use a different cyl for coil on plug coils you can use that method also. Start with the easiest swaps and see what you get.

 

Since you replaced practically everything (hopefully with quality parts), you need to see if your # 3 injector is receiving power (12v) on one leg and being pulsed to ground potential by the computer on the other leg when it is to energize. How exactly do you know if the plug is firing? By visually saying it looks like new, means nothing. I hope you saved all those parts because they probably good and better in quality than what you put in.

 

Most folks are not aware that so many imported parts are not of the best quality and some are defective right out of the box. They might look nice, but,,,, !

There are a lot of domestic aftermarket suppliers that offer decent quality, the object is to know which ones.

Some places spend more on advertising than quality and good parts may cost a little more, but there is nothing like doing the job over because we chose the cheapest price parts. What we are hoping to establish is, " I just replaced that part with new, so it can't be that", can take you for quite a ride.
Most folks don't look to see the place of manufacture when purchasing parts and that should be given some consideration.

 

Truer words have never been spoken!