Diagnosing the state of the spark plugs is an effective method for elucidating the cause of engine troubles.
The flowing trouble can be caused by engine defects.
Spark plug state
· Starting defect
· Misfiring when idling
· Misfiring during normal running
· Misfiring only when running at high speed or when accelerating suddenly
· Loss of power when running at high speed or under high load
· Piston breakdown
· Trouble other than with the engine