Check the plugs for deposits and wear. Look carefully at the center electrode protrudes through the center of the porcelain. If the center electrode is eroded or rounded, replace the spark plugs. If the plugs 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 are sometimes found in service stations. These machines do a good job of cleaning the spark plug, although they tend to remove the protective anti-corrosive coating on the spark plug threads. They also cause the surface of porcelain around the center electrode to become slightly porous, allowing deposits to bond more easily to the porcelain. If a plug cleaner is used to clean the plugs, be sure the plug is thoroughly cleaned. The abrasive material used in the spark plug cleaners is very hard, and if allowed to enter the engine-s combustion chamber, could cause internal damage. An acceptable job of cleaning the spark plug can be accomplished by using a stiff wire brush. Once the plugs are cleaned, the spark plug gap must be checked and reset to specification.
Check spark plug gap before installation. Using a suitable spark plug gap gauge, check the spark plug gap. Make sure the L-shaped electrode connected to the body of the spark plug is parallel to the center electrode. If necessary, adjust the L-shaped electrode to attain the correct gap and proper alignment. Make sure to use the specified size wire gauge, which must pass between the electrodes with a slight drag and the next larger size should not be able to pass, while the next smaller size should pass freely. When adjusting a spark plug gap, always set the gap to the minimum specification to allow for electrode wear. Refer to the following information pertaining to spark plug gap.
Check, but do not adjust the spark plug gap. The spark plug gap should be 0.039-0.043 inches (1.0-1.1mm). If the spark plug gap exceeds 0.051inches (1.3mm), replace the spark plug.
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 because the reading may be inaccurate. A round-wire type gapping tool is the best tool for checking the plug gap. The correct gauge should pass through the electrode gap with a slight drag. If 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 this to adjust the side electrode until the proper clearance is obtained. Never attempt to bend the center electrode. Be careful not to bend the side electrode too far or too often as it may weaken and break off inside the engine, requiring removal of the cylinder head to retrieve it.
Removal & Installation
Some models use a coil over plug ignition system. Each of the spark plugs has its own ignition coil which mounts directly above the spark plug and eliminates the need for a distributor, distributor cap, rotor and spark plug wires. Because the ignition coils are placed above the spark plugs, the coils must be removed before the spark plugs can be accessed.
- Disconnect the negative battery cable, note the radio security code and, if the vehicle has been run recently, allow the engine to thoroughly cool.
- Remove the intake manifold cover.
- Remove the trim covers located above the cylinder head covers.
- Label the electrical terminals for each ignition coil, and detach the electrical connector from each ignition coil.
- Remove the fasteners securing each ignition coil to the cylinder head cover, then remove the coils.
Using a spark plug socket equipped with a rubber insert to properly hold the plug, turn the spark plug counterclockwise to loosen and remove the spark plug from the threaded hole in the cylinder head.
WARNINGAvoid using a flexible extension on the spark plug socket. A flexible extension may allow a shear force to be applied to the plug. A shear force could break the plug off in the cylinder head, leading to costly repairs.
Inspect each ignition coil for damage, or deterioration. Make sure the coils are clean, and free of debris, such as engine oil. If a damaged coil is found, it should be replaced.
WARNINGThe original equipment spark plugs installed in the 3.5L V-6 engine are platinum tip spark plugs, and the plug gap must not be adjusted.
- Using a wire feeler gauge, check, but do not adjust the spark plug gap. When using a gauge, the proper size should pass between the electrodes with a slight drag. The next larger size should not be able to pass, while the next smaller size should pass freely.
- The spark plug gap should be 0.039-0.043 inches (1.0-1.1mm). If the spark plug gap exceeds 0.051inches (1.3mm) replace the spark plug.
- Apply a light coating of an anti-seize compound to the spark plug threads.
Carefully thread the plug into the threaded spark plug hole by hand. If resistance is felt before the plug is almost completely threaded, back the plug out and begin threading again. In tight, hard to reach areas, a small piece of rubber hose pressed onto the spark plug can be used as a threading tool. The rubber hose will hold the plug and while twisting the end of the hose, and the hose will be flexible enough to twist before allowing the plug to crossthread.
WARNINGDo not use any excessive force when beginning to install the plugs. Always carefully thread the plug by hand or by using a rubber hose to prevent the possibility of crossthreading and damaging the cylinder head threads.
- Carefully tighten the spark plug to 13 ft. lbs. (18 Nm).
- Install the ignition coils, then attach the electrical connector to each ignition coil.
- Install the trim covers onto the cylinder head covers and the intake manifold cover.
- Connect the negative battery cable and enter the radio security code.