Spark Plug: Testing and Inspection

Spark Plug Inspection:

1. Inspect the electrodes and ceramic insulator for wear, overheating or fouling.

Overheated 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

Checking Spark Plug Electrode Gap:

2. Adjust the gap to 1.0 - 1.1 mm (0.039 - 0.043 in) with a suitable gapping tool.
3. Replace the plug if it is fouled or worn.
4. Apply a small quantity of anti-seize compound to the plug threads.
5. Screw the plugs into the cylinder head finger-tight, then torque them to 18 Nm (13 ft.lb).