Sunday, June 1, 2008



Spark plug transmits an extremely high voltage across the electrodes to produce sparks, which ignite and explode the air-fuel mixture compressed in cylinders of a petrol engine.

Necessity of maintenance / What happens if not done

With use ,the spark plug electrodes experiance a gradual erotion and widening of the gap between them, making spark generation difficult. At the same time , combution deposits on the insulator tip and the electrodes cause short circuit of the current, resulting in sparks between impropper portions.

If the plugs are worn, the engine performance will decrease and fuel economy will become worse.

If the ignition timing is advanceed too much , or retarded too much,it will cause the engine's power decrease.

Maintenance Interval

Spark plug ( conventional type )
  • Inspect and correct or replace as necessary every 10,000km /6 months and replace every 20,000km /12 months ,whichever comes first.(When using leaded petrol , it is recomendable to replace spark plug earlier( to a half or a third) than the one using unleaded petrol.)

Spark plug ( Platinum- tipped type )

  • Replace every 100,000 km

Ignition wires

  • Inspect and correct or replace as necessary every 40,000km / 24 months, whichever comes first.

Ignition timing

  • For emission-controlled engine , adjust the timing every 20,000km / 24 months, whichever comes first.
  • For non emission-controlled engine , adjust the timing every 10,000km / 6 months, whichever comes first.
  • In the case of some latest engine , ignition timing adjustmentis not necessary.

Maintenance job

  1. Clean the plug with wire brush and check for damage or cracks ( for platinum type or Iridium type do not clean )
  2. Check plug gap with plug gap gauge (Only conventional type )
  3. Inspect wire for cracks, damage,burned terminals and for improper fit.
  4. Measure the resistance of wires and check for intermitent breaks.
  5. Check ignition timing and adjust as necessary.

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