How to Replace the Spark Plugs on a 2003 Ford Ranger 4.0
- 1). Check the gap on the bottom of all six new Motorcraft AGSF34FP, or equivalent spark plugs with a spark plug gap tool. The gap required for the 4.0-liter engine is 0.061 to 0.068 inches. Exchange any incorrectly gapped plugs for new ones, as these plugs are not adjustable.
- 2). Loosen the lug nuts on the right front wheel with a ratchet and socket. Raise the front of the Ranger with a floor jack and slide jack stands under its frame rails. Lower the Ford onto the jack stands. Remove the lug nuts from the right front wheel and pull the wheel off the hub.
- 3). Pry the five retaining pins from the top of the right front-wheel well liner with a flat-head screwdriver and pull the wheel well liner from the vehicle, exposing the right side spark plugs and wires.
- 4). Pull upward on the thick rubber boot on one spark plug wire with a slight twisting motion to remove it from the spark plug. Remove the spark plug with a ratchet and spark plug socket. Pull the old spark plug from the socket – a rubber insert holds it inside the socket.
- 5). Press a new Motorcraft AGSF34FP, or equivalent spark plug into the spark plug socket until the rubber insert holds it in place. Hand-tighten the spark plug into the engine, using the spark plug socket. Tighten the spark plug to 13 foot-pounds with a torque wrench and spark plug socket.
- 6). Inspect the unplugged spark plug wire for any defects, including burn marks, cracks, splits or breakage. If any defects exist, replace all of the wires one-by-one – replacing them this way greatly lowers your chances of mixing up the firing order.
- 7). Squeeze a small amount of dielectric grease meeting Ford specification ESE-M1C171-A into the spark plug wire boot. Spread the dielectric grease around the inside of the boot with a small flat-head screwdriver.
- 8). Line up the spark plug wire boot with the top of the spark plug and press the boot onto the spark plug until you feel it click into place.
- 9). Repeat steps 4 through 8 to replace the remaining two spark plugs on the right side of the engine.
Reinstall the right front-wheel well liner, lining up its pinholes with those in the wheel well. Press the pins into the pinholes to secure the wheel well liner in place.
Set the wheel back on the right front hub and hand-tighten the lug nuts. Raise the truck off the jack stands with a floor jack and remove the jack stands. Lower the Ranger to the ground and tighten the lug nuts, in a crisscross pattern, to 100 foot-pounds with a torque wrench and socket.
Remove and replace the three spark plugs on the left side of the engine by following steps 4 through 8 on each spark plug.