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Home >> Mazda >> 2021 >> CX-9 Signature >> Repair and Diagnosis >> Engine Performance >> System >> Symptom Troubleshooting - Engine >> No. 28 Spark Plug Condition >> Notes
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No. 28 Spark Plug Condition: Notes

NO. 28 SPARK PLUG CONDITION (SKYACTIV-G 2.5T) DESCRIPTION AND POSSIBLE CAUSE

28 SPARK PLUG CONDITION
DESCRIPTION
  • Incorrect spark plug condition.
POSSIBLE CAUSE
NOTE:
  • Inspecting the spark plug conditions can determine whether a problem is related to a specific cylinder or possibly all cylinders.
Wet/carbon stuck on specific plug:
  • Spark-Weak, not visible
  • Air/fuel mixture-Excessive fuel injection volume
  • Compression-No compression, low compression
  • Malfunction spark plug

    Grayish white with specific plug:

  • Air/fuel mixture-Insufficient fuel injection volume
  • Malfunction spark plug

    If a spark plug on a specific cylinder is damaged or corroded:

  • Malfunction spark plug
    • Damage or corrosion due to pre-ignition or knocking Wet/carbon is stuck on all plugs:
  • Spark-Spark weak
  • Air/fuel mixture-Too rich, excessive fuel line pressure
  • Erratic signal to PCM
    • ECT sensor No. 1 or related circuit malfunction
    • MAF sensor or related circuit malfunction
    • A/F sensor or related circuit malfunction
      • HO2S or related circuit malfunction
  • Compression-Low compression
  • Restriction in intake/exhaust system

    Grayish white with all plugs:

  • Erratic signal to PCM
    • ECT sensor No. 1 or related circuit malfunction
    • MAF sensor or related circuit malfunction
    • A/F sensor or related circuit malfunction
      • HO2S or related circuit malfunction
  • Air/fuel mixture-Too lean, insufficient fuel line pressure
    WARNING:
    • The following troubleshooting flow chart contains the fuel system diagnosis and repair procedures. Read the following warnings before performing the fuel system services:
      • Fuel vapor is hazardous. It can easily ignite, causing serious injury and damage.

        Always keep sparks and flames away from fuel.

      • Highly pressurized fuel may spray out if the fuel line is cut. Due to the following dangers occurring with a fuel spray, always complete the "Fuel Line Safety Procedure" to prevent the fuel from spraying. (See BEFORE SERVICE PRECAUTION [SKYACTIV-G 2.5T] .)
  • Fuel may cause irritation if it comes in contact with skin and eyes.
    • If fuel ignites and causes a fire, it may lead to serious injury or death, and damage to property and facilities.
    CAUTION:
    • Disconnecting/connecting the quick release connector without cleaning it may cause damage to the fuel pipe and the quick release connector. Always clean the quick release connector joint area before disconnecting/connecting, and make sure that it is free of foreign material.