Safety Warning
DIY auto repair can cause serious injury, fire, or vehicle damage. These guides are for informational purposes only. Always follow OEM torque specs, wear PPE, and consult a certified mechanic if you are unsure. You are solely responsible for your safety.
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HOMESERVICE MANUALSCHEVROLET2001METRO L4-079 1.3L VIN 2 MFIREPAIR AND DIAGNOSISPOWERTRAIN MANAGEMENTIGNITION SYSTEMSPARK PLUGDESCRIPTION AND OPERATION
2001 Chevrolet Metro L4-079 1.3L VIN 2 MFI
Spark Plug: Description and Operation
2001 Chevrolet Metro L4-079 1.3L VIN 2 MFISECTION Description and Operation
NOTE: Allow the engine to cool down before removing the spark plugs. Removing the spark plugs from an engine at operating temperature may damage the spark plug threads in the aluminum cylinder head.
Normal service is considered to be a mixture of idling, slow-speed and high-speed driving. Occasional or intermittent highway driving is needed for good spark plug performance. The higher combustion temperature generated during highway driving burns away any deposits of carbon or oxides that build up from frequent idling or continuous stop-and-go driving. Spark plugs are protected by an insulating nipple made of special heat-resistant material, which covers the spark plug terminal and extends downward over a portion of the plug insulator. These nipples prevent flash-over which causes engine misfiring. Do not mistake corona discharge for flash-over, or a shorted insulator. Corona discharge is a steady blue light appearing around the insulator, just above the shell crimp. It is the visible evidence of a high-tension field and has no effect on ignition performance.
Spark plugs must operate within certain temperature limits if they are to provide the performance and service life expected. The spark plug selected for an engine is based on the normal service for which the engine was designed and may not perform satisfactorily under other than normal operating conditions. For almost exclusive city driving, a spark plug one step higher in the heat range might deliver longer service life than the spark plug recommended. Conversely, a spark plug one step colder will perform better for heavy loads or continual high-speed driving.
There are three rules to follow when selecting spark plugs for an engine in good condition.
1. Select a spark plug with the specified heat range.
2. If spark plug overheating occurs, select a spark plug that is one heat range lower than the specified heat range.
3. If fouling is a problem, select a spark plug that is one heat range higher than the specified heat range.
Spark Plug Usage:
Normal service is considered to be a mixture of idling, slow-speed and high-speed driving. Occasional or intermittent highway driving is needed for good spark plug performance. The higher combustion temperature generated during highway driving burns away any deposits of carbon or oxides that build up from frequent idling or continuous stop-and-go driving. Spark plugs are protected by an insulating nipple made of special heat-resistant material, which covers the spark plug terminal and extends downward over a portion of the plug insulator. These nipples prevent flash-over which causes engine misfiring. Do not mistake corona discharge for flash-over, or a shorted insulator. Corona discharge is a steady blue light appearing around the insulator, just above the shell crimp. It is the visible evidence of a high-tension field and has no effect on ignition performance.
Spark plugs must operate within certain temperature limits if they are to provide the performance and service life expected. The spark plug selected for an engine is based on the normal service for which the engine was designed and may not perform satisfactorily under other than normal operating conditions. For almost exclusive city driving, a spark plug one step higher in the heat range might deliver longer service life than the spark plug recommended. Conversely, a spark plug one step colder will perform better for heavy loads or continual high-speed driving.
There are three rules to follow when selecting spark plugs for an engine in good condition.
1. Select a spark plug with the specified heat range.
2. If spark plug overheating occurs, select a spark plug that is one heat range lower than the specified heat range.
3. If fouling is a problem, select a spark plug that is one heat range higher than the specified heat range.
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When to See a Mechanic
Stop DIY work and contact a certified mechanic immediately if any of the following apply:
- • You smell fuel, burning insulation, or see smoke.
- • Brakes feel soft, pull hard to one side, or make grinding noises.
- • The engine overheats, stalls repeatedly, or misfires under load.
- • You are missing required tools, torque specs, or safe lifting equipment.
- • You are not confident in the next step or safety outcome.