Isuzu 2008MY N Series, Руководство по ремонту

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Engine Control System (4HK1) 1A-361
Abnormal Combustion Noise
Checks Action
Definition:
A mild to severe ping, usually worse under acceleration. The engine makes sharp metallic knocks that change with
the throttle opening.
Preliminary Checks • Diagnostic System Check - Engine Controls.
• Ensure the vehicle has an actual problem.
• Inspect for smoke associated with the combustion noise.
• Inspect the fuel quality (cetane index).
• Inspect the programmed fuel injector ID code for each cylinder.
• Inspect the Scan Tool Data List in this section.
• Inspect the Service Bulletin.
Sensor Checks Inspect the engine control sensors for the following conditions. Refer to the
Scan Tool Data List in this section.
• Compare the Coolant Temperature with the Intake Air Temperature (IAT)
and Fuel Temperature (FT) parameters on a cold engine condition. If the
difference among temperature reading is more than 5
°
C (9
°
F) on a cold
engine, check for high resistance in each circuit or for a skewed sensor.
Notice: The mass air flow (MAF) sensor is heated and as a result the IAT may
indicate a higher than normal intake air temperature if the ignition switch is
being ON.
• Observe the Fuel Rail Pressure (FRP) Sensor parameter with the engine
OFF. The FRP Sensor should read 0.9 to 1.0 volt with the ignition switch
ON and engine OFF after the engine has stopped running for a minimum of
1 minute. If not, check for high resistance in each circuit or for a skewed
sensor.
• Observe the Fuel Rail Pressure and Desired Fuel Rail Pressure parameter
between idle and W.O.T. (accelerator pedal full travel) in Neutral. Fuel Rail
Pressure parameter should follow within
±
5 MPa (
±
725 psi) quick enough.
• Crankshaft position (CKP) sensor is tight and the sensor rotor is not
damaged.
Fuel System Checks • If excessive smoke is present, check for a stuck open fuel injector. Inspect
for fuel leakage into the combustion chamber.
• Inspect the fuel injectors. Remove the injectors and visually inspect.
• Perform the Cylinder Balance Test with a scan tool.
• Perform the Injector Force Drive with a scan tool.
• Observe the Fuel Compensation for each cylinder at idle on the scan tool.
Engine Mechanical Checks Inspect the engine mechanical for the following conditions. Refer to the
Section 1B Engine Mechanical.
• Poor cylinder compression.
• Incorrect basic engine parts such as camshaft, cylinder head, pistons, etc.
• Inspect for any excessive oil entering combustion chamber.
Additional Checks • Inspect other possible causes that can make similar noise such as loose
component parts, bracket, mount and weak clutch damper spring.
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