Ford introduced the F-250 in 1953, as the automaker changed the names on all three of its full-sized pickups. In the 1997 model year, Ford introduced a new engine for the F-250 and F-350: the 6.8-liter V-10. The 6.8-liter equipped 2004 Ford F-250 produced 310 horsepower and 425 foot-pounds of torque. This engine utilized Ford's famed coil-on-plug ignition system, which positions a coil on top of each spark plug, delivering a reliable spark and minimal resistance. Ford recommends replacing the spark plugs in the 2004 Ford F-250 every 100,000 miles.
Check the gap between the two electrodes on all 10 of the new Motorcraft AWSF-22E (or equivalent) spark plugs, using a spark plug gap tool. The 6.8-liter engine requires a gap of 0.052 to 0.056 inches, so exchange any incorrectly-gapped plugs for a new ones. The spark plugs recommended for the 2004 F-250 are not adjustable.
Trace the air intake hose from the air filter box toward the engine. Remove the two smaller hoses -- idle air control supply and crankcase ventilation hoses -- by pulling them from the air intake hose.
Loosen the hose clamps at either end of the air intake hose, using a Phillips screwdriver, and pull the hose from the engine compartment.
Unplug the wiring harness from the top of the coil pack by pressing the locking button and pulling the harness from the coil pack. Remove the bolts securing the coil pack to the engine, using a ratchet and socket, and pull the pack upward, with a slight twisting motion, to remove it.
Remove the spark plug, using a ratchet, 6-inch extension and a spark plug socket. Pull the old spark plug from the spark plug socket and insert the new plug into the socket.
Hand-tighten the new spark plug into the engine, using the spark plug socket and 6-inch extension. Apply 11 foot-pounds of torque to the spark plug with a torque wrench.
Apply a thin coat of dielectric grease inside the rubber boot on the bottom of the coil pack and set the coil pack on the spark plug. Press the coil pack downward, toward the spark plug, until it clicks into place.
Reconnect the wiring harness to the top of the coil pack and tighten the coil pack bolt to 4 to 5 foot-pounds, using a torque wrench and socket.
Repeat steps 4 through 8 until you replace all 10 spark plugs.
Reinstall the air intake hose and tighten the hose clamps, using a Phillips screwdriver. Plug the IAC and CCV hoses back into their respective ports on the air intake hose.
