Chevrolet Aveo 2009 Service Manual page 63

Document ID: 1456106
4. Inspect (3) for evidence of improper arcing.
• Measure the gap between the center electrode (4) and the side electrode (3) terminals.
An excessively wide electrode gap can prevent correct spark plug operation.
• 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.
• Inspect for signs of tracking that occurred near the insulator tip instead of the center
electrode (4).
• Inspect for a broken or worn side electrode (3).
• Inspect for a broken, worn, or loose center electrode (4) by shaking the spark plug.
- A rattling sound indicates internal damage.
- A loose center electrode (4) reduces the spark intensity.
• Inspect for bridged electrodes (3, 4). Deposits on the electrodes (3, 4) reduce or
eliminates the gap.
• Inspect for worn or missing platinum pads on the electrodes (3, 4), if equipped.
• Inspect for excessive fouling.
5. 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.
Spark Plug Visual Inspection
• Normal operation--Brown to grayish-tan with small amounts of white powdery deposits are
normal combustion by-products from fuels with additives.
• Carbon fouled--Dry, fluffy black carbon, or soot caused by the following conditions:
- Rich fuel mixtures
• Leaking fuel injectors
• Excessive fuel pressure
• Restricted air filter element
• Incorrect combustion
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7/6/2010