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Home >> Kia >> 2016 >> Cadenza Base >> Repair and Diagnosis >> Engine Performance >> System >> Engine Control System Diagnosis (2 Of 3) >> DTC P0300: Random/Multiple Cylinder Misfire Detected >> System Inspection
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System Inspection

■ Misfire Inspection 

  1. Check the cylinder where the misfire occurs after replacing the ignition coil of the cylinder where the misfire has occurred with the ignition coil of the other cylinder.
  2. Does the misfiring cylinder change?

    YES 

    NO 

    • Go to "Check Air Leakage" below.

■ Ignition coil waveform inspection 

  1. Ignition "ON" and engine "ON".
  2. Measure the voltage between control terminal of ignition soil harness connector and chassis ground.

    Specification:  Refer to Fig 1

    Fig 1: Screen Display - Engine Idle After Warm Up
    G11790513Courtesy of KIA MOTORS AMERICA, INC.

    Spark retention time - Approx. 1.2ms

    CH. A - Ignition Max 31V

  3. Is the measured waveform within specification?

    YES 

    • Repair as necessary except for the ignition coils and go to "Check Air Leakage" procedure below.

    NO 

    • Go to "Check Spark Plug" procedure.

■ Check Spark Plug 

  1. Remove cylinder's spark plugs
  2. Visually/physically inspect the following items:
    • Damaged insulation, Worn electrodes, Oil or fuel fouled, Loose terminals and cracks.
    • Check for plug gap: 1.0 - 1.1 mm (0.039 - 0.043 in.)
    • Check if the spark plug for the relevant cylinder is lighter in color than the other plugs.
  3. Has a problem been found in any of the above areas?

    YES 

    NO 

    • Go to "Check Air Leakage" below.

■ Check Air Leakage 

  1. Visually/physically inspect the air leakage in intake/exhaust system as following items,
    • Vacuum hoses for splits, kinks and improper connections.
    • Throttle body gasket
    • Gasket between intake manifold and cylinder head
    • Seals between intake manifold and fuel injectors
    • Exhaust system between exhaust manifold and Three way catalyst for air leakage.
  2. Has a problem been found in any of the above areas?

    YES 

    NO 

    • Go to "Check for air leakage in Positive Crankcase Ventilation Valve (PCV)".

■ Check for air leakage in Positive Crankcase Ventilation Valve (PCV) 

  1. Remove PCV valve from cylinder head cover by pulling ventilation hose.
  2. With engine idling block PCV valve opening.
  3. Verify that vacuum is felt.
  4. Remove PCV valve.
  5. Blow through valve from port "A" and verify that air comes out of port "B".
  6. Blow through valve from port "B" and verify that no air comes out of port "A".
  7. Has a problem been found in any of the above areas?

    YES 

    NO 

    • Go to "Check Compression pressure" below.

■ Check Compression pressure 

  1. Warm up the engine to normal operating temperature.
  2. Disconnect the spark plug cables and remove the spark plugs.
  3. Crank the engine to remove any foreign material in the cylinders.
  4. Put compression pressure gauge into spark plug hole.
  5. Crank the engine with throttle valve wide open and check compression pressure at each cylinder.

    Specification:  1, 029kPa (10.5kgf/cm2 , 149psi) (250~400 rpm)

  6. Is compression pressure for each cylinder displayed within specifications?

    YES 

    • Go to "Check Timing" below.

    NO 

    • 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 remains the same, the cause is a burnt or defective valve seat, or pressure is leaking from the head gasket. Repair as necessary. Go to "VERIFICATION OF VEHICLE REPAIR " procedure

■ Check Timing 

  1. IG "OFF"
  2. Monitor these signal waveforms from CAM and Crankshaft position Sensor are correctly aligned.

    Reference: The 17th CKP signal after the missing tooth is aligned with the high voltage CMP signal.

    Fig 2: Screen Display - Signal Waveform From CAM And Crankshaft Position Sensor
    G11790514Courtesy of KIA MOTORS AMERICA, INC.
    Fig 3: Cam, Crank And Oil Pump Sprocket Timing Marks
    G11790515Courtesy of KIA MOTORS AMERICA, INC.
  3. Are all timing marks aligned correctly?

    YES 

    • Go to "Check Fuel Pressure" below

    NO 

    • Check that Cam, Crank and Oil pump sprocket timing marks are correctly aligned. Repair or readjust as necessary. Go to "VERIFICATION OF VEHICLE REPAIR " procedure

■ Check fuel pressure 

NOTE:
  1. Be cautious fuel is explosive and an empty fuel tank can still contain explosive gases. When working on fuel systems make sure to supply adequate ventilation to the work area. Do not smoke, and keep sparks and open flames away.
  2. The fuel system remains under pressure when the engine is not running. Release fuel system pressure before disconnecting any fuel line to reduce the chance of personal injury or fire damage to vehicle components.
  1. IG "OFF". Disconnect Fuel Pump Relay in Junction Box.
  2. Start engine and wait until it stalls.
  3. IG "OFF". Connect Fuel Pump Relay.
  4. Install the fuel pressure gauge to the delivery pipe with the fuel pressure gauge adaptor. (Refer to FUEL PRESSURE TEST (LOW PRESSURE SYSTEM) )
  5. Activate the fuel pump, check that there are no fuel leaks from the pressure gauge or fuel system.
  6. Measure the fuel pressure at idle.

    Specification:  400 ~ 600 kPa (4.07 ~ 6.12 kg/cm2 , 58 ~ 87 psi)

  7. Is the measured fuel pressure within specifications?

    YES 

    • Substitute with a known - good PCM and check for proper operation. If the problem is corrected, replace PCM and go to "VERIFICATION OF VEHICLE REPAIR " procedure.

    NO 

Condition Possible Cause
Fuel Pressure is too low Fuel filter, fuel pressure regulator, in-tank fuel hose or the fuel pump
Fuel Pressure is too high Fuel pressure regulator, hose or pipe
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