99 Expedition 4.6 Misfire

I have a 304 Code... w/ intermittent misfire. I have replaced plug & wire. Pulled injector and blew it out and replaced and ran a drop test on 1-4, which checked O.K. Afterwards, drove for about 30 mi w/ no
misfire and running smooth. Next morning cranked up w/ miss again. Wondering if it could be trash in fuel rail or what is the likelihood of coil pack going bad? Ideas?
Thewdawg
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Thewdawg wrote:

My 4.6 is notorious for very small water leaks that manage to leak into the spark plug chamber. I would check all the plug wires for moisture.
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Thewdawg wrote:

Coil on plug? If so swap the #4 COP and boot out to an adacent cylinder and see if the code follows it. Look for carbon tracks on the boot.
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