Jeezbus.. 73K on the plugs...
3 year old wires..
where to start? you said no unusual COLOR... you checked the gap, I assume? (.054) The rear bank (back three) tend to wear nearly twice as fast due to waste spark ignition system in this car.
If you replace them, use only OEM Motorcraft, or Autolite Double plats (part number is "APP764") (DOUBLE PLATS!!!)... I'll say it again.. DOUBLE PLATS... not +4, not singles, not fine wire... double plats..
OEM motorcraft wires are preferred, though ford racing wires (9mm) work well, most of the time, too.. some light dremeling is required to the wire holders to get them to snap in to them, though.. (free, and quick..)
Ray
