- Ensure that the correct spark plug is installed. An incorrect spark plug causes driveability conditions.
Ensure that the spark plug has the correct heat range. An incorrect heat range causes the following conditions:
Spark plug fouling-Colder plug
Inspect the terminal post (1) for damage.
Inspect for a bent or broken terminal post (1).
Inspect the insulator (2) for flashover or carbon tracking, soot. This is caused by the electrical charge traveling across the insulator (2) between the terminal post (1) and ground. Inspect for the following conditions:
Inspect the spark plug boot for damage.
- Inspect the insulator (2) for cracks. All or part of the electrical charge may arc through the crack instead of the electrodes (3, 4).
Inspect for evidence of improper arcing.
Measuring the gap between the center electrode (4) and the side electrode (3) terminals. An excessively wide electrode gap can prevent correct spark plug operation.
- Normal operation-Brown to grayish-tan with small amounts of white powdery deposits are normal combustion by-products from fuels with additives.
Carbon fouled-Dry, fluffy black carbon, or soot caused by the following conditions:
Rich fuel mixtures: Leaking fuel injectors, excessive fuel pressure, restricted air filter element, incorrect combustion.
- Deposit fouling-oil, coolant, or additives that include substances such as silicone, very white coating reduces the spark intensity. Most powdery deposits will not affect spark intensity unless they form into a glazing over the electrode.
Inspection & Gapping
The ignition timing is preset and cannot be adjusted.
Removal & Installation
Remove the ignition coils.
CAUTIONWear safety glasses when using compressed air, as flying dirt particles may cause eye injury.
WARNINGClean the spark plug recess area before removing the spark plug. Failure to do so could result in engine damage because of dirt or foreign material entering the cylinder head, or by the contamination of the cylinder head threads. The contaminated threads may prevent the proper seating of the new plug. Use a thread chaser to clean the threads of any contamination.
Clean the spark plug recesses with low pressure air.
CAUTIONAllow the engine to cool before removing the spark plugs. Attempting to remove the spark plugs from a hot engine may cause the plug threads to seize, causing damage to cylinder head threads.
- Remove the spark plugs from the cylinder head.
Inspect the spark plugs.
Measure the spark plug gap on the spark plugs to be installed. Compare the measurement to the gap specifications, 0.042 in (1.08 mm).
WARNINGBe sure that the spark plug threads smoothly into the cylinder head and the spark plug is fully seated. Use a thread chaser, if necessary, to clean threads in the cylinder head. Cross-threading or failing to fully seat the spark plug can cause overheating of the plug, exhaust blow-by, or thread damage.
- Install the spark plugs to the cylinder head. Tighten the spark plugs to 13ft. lbs. (18 Nm).
- Install the ignition coils.