The Toyota 4.7-liter engine uses a coil-on-plug system. This means that each spark plug has its own coil. The coil sits on top of the spark plug, eliminating the need for spark plug wires. Spark plugs should be replaced according to your maintenance schedule, even if they do not look like they need to be replaced. Always replace all eight spark plugs at the same time to ensure optimal engine performance.
Remove the wiring harness connector on each of the coils by pressing in on the plastic tabs and pulling the plug off the coil. Working with one coil and one spark plug at a time, unbolt the coil and pull it off the engine.
Remove the spark plug using the 16-mm spark plug socket. Insert a spark plug into the spark plug hole and start turning it by hand. After four or five turns, use the socket to tighten it firmly, but no more than 13 ft.-lbs. of torque. Do not overtighten the plug, as you could crack the porcelain.
Replace the coil, tightening the bolts firmly. Plug the wiring harness connector in. Repeat the process for all eight plugs.
