Yukon/Denali 2WD V8-4.8L VIN V (2005)
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Inspect for the correct spark plug torque. Refer to Ignition System Specifications. 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.
