Sierra 1500 4WD V8-6.0L (2007)
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Inspect for evidence of improper arcing.
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Measure the gap between the center electrode (4) and the side electrode (3). An excessively wide electrode gap can prevent correct spark plug
operation.
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Inspect for the correct spark plug torque. Insufficient torque can prevent correct spark plug operation. An over torqued spark plug, causes the
insulator (2) to crack.
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Inspect for signs of tracking that occurred near the insulator tip instead of the center electrode (4).
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Inspect for a broken or worn side electrode (3).
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Inspect for a broken, worn, or loose center electrode (4) by shaking the spark plug.
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A rattling sound indicates internal damage.
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A loose center electrode (4) reduces the spark intensity.
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Inspect for bridged electrodes (3, 4). Deposits on the electrodes (3, 4) reduce or eliminates the gap.
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Inspect for worn or missing platinum pads on the electrodes (3, 4), if equipped.
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Inspect for excessive fouling.
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Inspect the spark plug recess area of the cylinder head for debris. Dirty or damaged threads can cause the spark plug not to seat correctly during
installation.
Visual Inspection
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Normal operation - Brown to grayish-tan with small amounts of white powdery deposits are normal combustion by-products from fuels with
additives.
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Carbon fouled - Dry, fluffy black carbon, or soot caused by the following conditions:
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Rich fuel mixtures
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Leaking fuel injectors
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Excessive fuel pressure
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Restricted air filter element
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Incorrect combustion
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Reduced ignition system voltage output
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Weak ignition coils
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Worn ignition wires
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Incorrect spark plug gap
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Excessive idling or slow speeds under light loads can keep spark plug temperatures so low that normal combustion deposits may not burn off.
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Deposit fouling - Oil, coolant, or additives that include substances such as silicone, very white coating, reduces the spark plug intensity. Most
powdery deposits will not affect spark plug intensity unless they form into a glazing over the electrode.