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Spark Plug Condition
Spark plug condition is indicative of engine operation. The spark plug
firing end condition should be read after the engine has been warmed up
and the vehicle has been driven at higher speeds. Immediately check the
spark plug for correct color.
Normal
The normal insulator tip is gray, tan or light brown. There will be few
combustion deposits. The electrodes are not burned or eroded. This indi-
cates the proper type and heat range for the engine and the service.
NOTE: The tip should not be white. A white insulator tip indicates over-
heating, caused by use of an improper spark plug or incorrect
carburetor/throttle body adjustments.
Wet Fouled
The wet fouled insulator tip is black. A damp oil film covers the firing
end. There may be a carbon layer over the entire nose. Generally, the
electrodes are not worn. General causes of fouling are excessive oil or
use of non-recommended injection oil.
WARNING
A hot exhaust system and engine can cause serious burns. Wear protective
gloves when removing a spark plug for inspection.