Troubleshooting

Diagnosing the state of the spark plugs is an effective method for elucidating the cause of engine troubles.

Normal

Trouble

The flowing trouble can be caused by engine defects.

Engine trouble

Case 1 Starting defect
Misfiring when idling
Misfiring during normal running
Diagnosis 1
Case 2 Misfiring only when running at high speed or when accelerating suddenly Diagnosis 2
Case 3 Loss of power when running at high speed or under high load Piston breakdown Diagnosis 3
Case 4 Trouble other than with the engine Diagnosis 4

Spark plug state

Diagnosis 1

<Case 1>
  • Starting defect
  • Misfiring when idling
  • Misfiring during normal running

Diagnosis 2

<Case 2>
  • Misfiring only when running at high speed or when accelerating suddenly

Diagnosis 3

<Case 3>
  • Loss of power when running at high speed or under high load
  • Piston breakdown

Diagnosis 4

<Case 4>
  • Trouble other than with the engine