Spark Plug: Description and Operation

Resistor spark plugs are used in this engine.

Remove the spark plugs and examine them for burned electrodes and fouled, cracked or broken porcelain insulators. Keep plugs arranged in the order in which they were removed from the engine. An isolated plug displaying an abnormal condition indicates that a problem exists in the corresponding cylinder. Replace spark plugs at the intervals recommended.

Faulty or fouled spark plugs may perform well at idle speed, but frequently fail at higher engine speeds. Faulty plugs can be identified in a number of ways: poor fuel economy, power loss, decrease in engine speed, hard starting and, in general, poor engine performance.

Spark plugs also malfunction because of carbon fouling, excessive electrode air gap, or a broken insulator. SEE Powertrain Management/Ignition System/Testing and Inspection/Procedures, for spark plug diagnosis.

CAUTION: Always tighten spark plugs to the specified torque. Over tightening can cause distortion and change the spark plug gap. Tighten spark plugs to 28 Nm (20 ft lb) torque.