I am trying to diagnose a number 4 misfire on a 4.7 liter with 287,000 miles. Below is what I've done so far. After each step I reset and cleared the code, and drove at least 50 miles to cycle the history out of it.

Replaced all the plugs with the correct champion plugs.
Replaced the coil on cylinder 4
Swapped the fuel injectors between cyl 4 and 6 to test for a bad injector.
I also ran two bottles of fuel injector cleaner in the tank.

The next thing I'm going to try is swapping the coil between 4 and 6 to see if the new coil is bad.

Anything else I can test? My PA inspection is overdue and it won't pass with a code showing.

Thanks in advance!

 

try a compression and or leak down test. how did you put all the 287,000 miles on? what year is it? mike

 

WOW!!!!!

You did your homework! A compression test and check the wiring harness. Also could be a crank shaft sensor or cam sensor.

 

Thanks x99j and hyrdashocker!

It's a 2001 I bought new. The majority of the miles are highway miles. I was in field sales for a few years. Overall the truck has been great! Other than brakes, tires, and ball joints...All I had to replace was a fuel pump, front bearings, and a computer.

I'll try the compression test and let you know what I find.

 

Sounds good.