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Home >> Kia >> 2023 >> Niro Plug-In Hybrid EX >> Repair and Diagnosis >> Engine Performance >> System >> Engine Control System Diagnosis (PHEV) (4 Of 9) >> DTC P0300-00: Random/Multiple Cylinder Misfire Detected >> System Inspection >> Engine Compression Test >> Measure the engine compression
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Measure the engine compression

  1. Warm up the engine to normal operating temperature.
  2. Remove the fuel pump fuse (20A).
  3. Wait until the engine stopped.
  4. Remove the ignition coils and spark plugs.
  5. Crank the engine to remove any foreign material in the cylinders.
  6. Put a compression pressure gauge into spark plug hole.
  7. Check compression pressure at each cylinder. (When the engine is rotated 10 times after fully charging the 12V battery)
    G15794530Courtesy of KIA MOTORS AMERICA, INC.
    Item Specification
    Standard 1225.83 kPa (12.5kg/cm2 , 177.79 psi) (200 to 250 RPM)
    Minimum 1078.73 kPa (11kg/cm2 , 156.46 psi)
    Difference between each cylinder Less than 98 kPa (1kg/cm2 , 14 psi)

    Good 

    • Fault might be intermittent and caused either by poor contact in connectors or wiring harness, or it has been repaired and control module memory is not cleared yet. Thoroughly check terminal of 12V battery, all connectors (and connections) for looseness, bending, corrosion, contamination, deterioration, and/or damage.
    • Repair or replace as necessary and Go to "VERIFICATION OF REPAIR " procedure.

    No Good 

    • Add a small amount of oil through the spark plug hole, and repeat above steps. If the addition of oil causes the compression to rise, the cause is a worn or damaged piston ring or cylinder inner surface.
    • If the compression on each cylinder is not the same or not similar a burnt or defective valve seat, worn head gasket and pressure rings can be the cause of vibration of engine.
    • Repair or replace as necessary and Go to "VERIFICATION OF REPAIR " procedure.
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