Grand Cherokee 2WD L6-4.0L VIN S (1997)
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Poor Ignition Output
NOTE: Cold fouling is normal when the vehicle is only operated for short periods. The spark plugs do not reach a high enough operating
temperature during short operating periods to burn fuel completely.
Electrode Gap Bridging
Fig. 6 Electrode Gap Bridging
Symptoms: Gap between the electrodes bridged by deposits.
Possible Causes:
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Loose deposits in the combustion chamber can accumulate on the spark plug electrodes during continuous stop and-go driving. Then when the
engine is suddenly subjected to a high torque load, the deposits partially liquefy and bridge the gap between the electrodes, short circuiting the
electrodes.
NOTE: 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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Normal Operating Conditions
