152k miles, 2 weeks ago the truck started missing. It has progressed to the point where it has stalled out 6 times while driving it short distances. Most of the time it starts back up, but one it took about an hour before it would start. I don't have a code reader yet, so I just replaced all coils and plugs (motorcraft). The issue is still not fixed and I'm just wondering if there is anything you guys think I could check easy/cheap. It doesn't miss at startup and runs great for the first minute, then starts missing and it's just a guessing game of when it will stall out on the road.

 

The old plugs looked good with the exception of cylinder 4. It was completely dry and almost white as new. I'm guessing that cyl is my issue.

 

Have you noticed any change in the antifreeze level?

When a cyl misfires for a period of time, the PCM will disable then fuel injector to prevent damage to the cat converter.

Was there any moisture in the spark plug well when you removed the spark plug for #4 cyl?