2500 4x4 Pickup V8-360 5.9L VIN 5 Magnum (1994)
Spark Plug Inspection
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Electrode gap bridging may be traced to loose deposits in the combustion chamber. These deposits accumulate on the spark plugs during
continuous stop-and-go driving. When the engine is suddenly subjected to a high torque load, the deposits partially liquefy and bridge the gap
between the electrodes. This short circuits the electrodes. Spark plugs with electrode gap bridging can be cleaned using standard procedures.
Heavy Colored Deposits
DESCRIPTION:
Colored coatings heavily deposited on the portion of the plug projecting into the chamber and on the side facing the intake valve.
POSSIBLE CAUSE
ACTION
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Leaking Valve Seals (1 or 2 cylinders)
- Check the valve seals. Replace if necessary. Clean, regap, and reinstall
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Overheating
Spark Plug Inspection
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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 can also cause spark plug overheating.
Premature Electrode Wear - Preignition Damage