Inspection & Gapping
Iridium and Platinum tipped spark plugs are designed to operate under normal vehicle operating conditions for up to 100,000 miles (160,000 kilometers) without periodic maintenance.
When no engine performance concerns are present, Iridium and Platinum tipped spark plugs should not be removed for periodic inspection and cleaning of threads, doing so may compromise the spark plug's ability to withstand their corrosive environment. The threaded area, although not sealed, serves as a protective environment against most harmful elements. Removing and cleaning spark plugs will introduce metallic debris and brush scrapings into the thread area which may further the corrosion process.
Chromate coated spark plugs should not be wire brushed or handled in any way once they are put in service. Chromium topcoats form a protective oxide on spark plugs that is not effective if scratched. Both coated and uncoated spark plugs will have the best chance of surviving a corrosive environment if they are left in position. Attempts to maintain spark plugs by removing them and cleaning the threads can actually create the corrosive condition that the procedure was intended to prevent.
- Ensure that the correct spark plug is installed. An incorrect spark plug causes drivability 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 for damage.
Inspect for a bent or a broken terminal post.
Inspect the insulator for flashover, for carbon tracking, and for soot. These conditions are caused by the electrical charge traveling across the insulator between the terminal post and the ground. Inspect for the following conditions:
Inspect the spark plug boot for damage.
- Inspect the insulator for cracks. All or part of the electrical charge may arc through the crack instead of the electrodes.
Inspect for evidence of improper arcing.
Measure the gap between the center electrode and the side electrode 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.
- Excessive idling or slow speeds during light loads can keep spark plug temperatures so low that normal combustion deposits may not burn off.
- Deposit Fouling--Oil, coolant, or additives that include substances such as silicone, or very white coating, reduce the spark intensity. Most powdery deposits will not affect the spark intensity unless the substances form into a glazing over the electrode.