Ignition System Description Spark Plug

The spark plugs are platinum tipped, tapered seat and resistor type. There are no gaskets on the spark plugs. When replacing the spark plugs, use only the type specified.

Idling, city, and highway driving are considered normal spark plug service. Occasional higher speed driving is needed for good spark plug performance. Driving at higher speeds increases combustion heat which burns away carbon or oxides which have built up from regular idling and stop-and-go city driving.

Insulated boots protect the spark plugs from heat. The boots cover the spark plug terminals and extend down over a portion of the spark plug insulators. The boots prevent spark plug flashover, which causes engine misfiring.

The corona is a steady blue light that appears around the insulator just above the shell crimp and can usually be detected only in darkness. The corona is sometimes mistaken for crossfire or a shorted insulator. The corona has no effect on engine performance.

The discharge may repel dust particles that leave a clear ring on the insulator just above the shell. This ring is not evidence that combustion gases have blown out between the shell and the insulator.

Ignition System Description Spark Plug Harness

The spark plug wire harnesses use carbon impregnated cord conductors. The conductors are encased in 8 mm (5/16 in) diameter silicone jackets. The jackets withstand very high temperatures and provide insulation for the high voltage of the system. Silicone spark plug boots form a tight seal on the spark plugs.

Ignition System Description Ignition Timing

The base timing is preset when the engine is manufactured. The timing cannot be adjusted. The timing is controlled by the ignition control and knock sensor systems through the powertrain control module (PCM). The knock sensor system retards the spark advance when detonation occurs.