Century L4-2.2L VIN 4 (1994)
Spark Plug: Description and Operation
Spark Plug Wire Routing
Resistor type, tapered seat spark plugs are used on all engines. No gasket is used on these tapered seat plugs. When replacing spark plugs, use only the
type specified.
Normal service is assumed to be a mixture of idling, slow speed, and high speed driving. Occasional or intermittent high-speed driving is needed for
good spark plug performance. It gives increased comustion heat, burning away carbon or oxides that have built up from frequent idling, or continual
stop-and-go driving.
Spark plugs are protected by an insulating nipple made of special heat-resistant material, which covers the spark plug terminal and extends downward
over a portion of the plug insulator. These nipples prevent flash-over, which causes engine misfiring. Do not mistake corona discharge for flash-over, or
a shorted insulator. Corona is a steady blue light appearing around the insulator, just above the shell crimp. It is the visible evidence of a high tension
field and has no effect on ignition performance. Usually it can be detected only in darkness. This discharge may repel dust particles, leaving a clear ring
on the insulator just above the shell. This ring is sometimes mistakenly regarded as evidence that combustion gases have blown out between shell and
insulator.
