Spark Plug: Testing and Inspection

Spark Plug Inspection:

1. Inspect the electrodes and ceramic insulator for:

Burned or worn electrodes may be caused by:
^ Advanced ignition timing
^ Loose spark plug
^ Plug heat range too low
^ Insufficient cooling

Fouled plug may be caused by:
^ Retarded ignition timing
^ Oil in combustion chamber
^ Incorrect spark plug gap
^ Plug heat range too high
^ Excessive idling/low speed running
^ Clogged air cleaner element
^ Deteriorated ignition coil or ignition wires

Spark Plug Inspection:

2. Check the electrode gap.
^ Adjust the gap with a suitable gapping tool.
^ Replace the plug if the center electrode is rounded as shown below:

3. Apply a small quantity of anti-seize compound to the plug threads, and screw the plugs into the cylinder head finger-tight. Then torque them to 18 N-m (1.8 Kgf.m, 13 lb.ft).