K Tahoe 4WD V8-4.8L VIN V (2000)
Spark Plug Visual Diagnosis Chart
^
Normal service is a mixture of idling, low speed, and high speed operation.
-
Occasional high speed driving is essential to good spark plug performance.
-
Increased combustion heat burns away excess carbon deposits, which accumulate from frequent idling or stop-and-go driving.
^
The heat resistant, insulating boot covers the spark plug terminal.
-
The boot extends over a portion of the spark plug insulator.
-
These boots prevent engine misfiring.
^
Corona discharge is a steady blue light appearing (in darkness) around the insulator, just above the shell crimp.
-
Do not mistake this for a shorted insulator.
-
This is visible evidence of a high-tension field.
-
This has no effect on ignition system performance.
-
This discharge repels dust particles.
-
This leaves a clear ring on the insulator just above the shell.
-
This is not evidence that combustion gases are escaping.
