Check the plugs for deposits and wear. If they are not going to be replaced, clean the plugs thoroughly. Remember that any kind of deposit will decrease the efficiency of the plug. Plugs can be cleaned on a spark plug cleaning machine, which can sometimes be found in service stations, or you can do an acceptable job of cleaning with a stiff brush. If the plugs are cleaned, the electrodes must be filed flat. Use an ignition points file, not an emery board or the like, which will leave deposits. The electrodes must be filed perfectly flat with sharp edges; rounded edges reduce the spark plug voltage by as much as 50%. Take care not to wear away the porcelain.
Check spark plug gap before installation. The ground electrode (the L-shaped one connected to the body of the plug) must be parallel to the center electrode and the specified size wire gauge (please refer to the Tune-Up Specifications chart for details) must pass between the electrodes with a slight drag.
Always check the gap on new plugs as they are not always set correctly at the factory. Do not use a flat feeler gauge when measuring the gap on a used plug, because the reading may be inaccurate. A round-wire type gapping tool is the best way to check the gap. The correct gauge should pass through the electrode gap with a slight drag. If you're in doubt, try one size smaller and one larger. The smaller gauge should go through easily, while the larger one shouldn't go through at all. Wire gapping tools usually have a bending tool attached. Use that to adjust the side electrode until the proper distance is obtained. Absolutely never attempt to bend the center electrode. Also, be careful not to bend the side electrode too far or too often as it may weaken and break off within the engine, requiring removal of the cylinder head to retrieve it.
Removal & Installation
4.4L & 4.6L Engines
- Disconnect the negative battery cable.
- Remove the engine acoustic cover by turning the fasteners 90 degrees counterclockwise.
- Remove the ignition coil covers.
- Disconnect the electrical connectors for the ignition coils.
- Remove the bolts and remove the ignition coils.
- Using a spark plug socket with an extension, remove the spark plug.
Using a spark plug socket with an extension, install the spark plug and tighten as follows:
- Plugs with M12x1.25 threads: to 17 ft. lbs. (23 Nm).
- Plugs with M14x1.25 threads: to 22 ft. lbs. (30 Nm).
- Install the ignition coil, ground strap and two bolts.
- Connect the electrical connector to the ignition coil.
- Install the ignition coil and acoustic covers.
- Connect the negative battery cable.