Grand Cherokee 2WD L6-4.0L VIN S (1997)
certain fuels. These additives are designed to change the chemical nature of deposits and decrease spark plug misfire tendencies. Notice that
accumulation on the ground electrode and shell area may be heavy, but the deposits are easily removed. Spark plugs with scavenger deposits can be
considered normal in condition and can be cleaned using standard procedures.
Shiny Yellow Glaze
DESCRIPTION:
Shiny yellow glaze coating on the insulator.
POSSIBLE CAUSE
ACTION
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Metal By-products Of Combustion
- Avoid sudden acceleration with wide open throttle after long periods of low speed driving.
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Wet Fouling or Gas Fouling
A spark plug coated with excessive wet fuel or oil is wet fouled. In older engines, worn piston rings, leaking valve guide seals or excessive cylinder wear
can cause wet fouling. In new or recently overhauled engines, wet fouling may occur before break-in (normal oil control) is achieved. This condition can
usually be resolved by cleaning and reinstalling the fouled plugs.
Wet Oily Deposits
Symptoms: Electrodes coated with excessive wet fuel or oil.
Possible Causes:
-
In older engines, wet fouling can be caused by worn rings or excessive cylinder wear.
-
In new or recently overhauled engines, fouling may occur before normal oil control is achieved. Break-in fouled spark plugs can be usually
be cleaned and installed.
White or Gray - Burned or Blistered Insulator
SPARK PLUG OVERHEATING
Spark Plug Overheating
Overheating is indicated by a white or gray center electrode insulator that also appears blistered. The increase in electrode gap will be considerably
in excess of 0.001 in. per 1000 miles of operation. This suggests that a plug with a cooler heat range rating should be used. Over advanced
ignition timing, detonation and cooling system malfunctions also can cause spark plug overheating. Also check for lean air-fuel mixture. Check the
torque value of the plugs to ensure good plug-engine seat contact.
