Isuzu 4ja1, Workshop Manual

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6E-250 Engine Control System (4JH1)
Checks Action
Engine Mechanical Check
Inspect the engine mechanical for the following conditions. Refer to the Engine
Mechanical section.
•
Inspect for poor cylinder compression. Proper compression is more than 2100 kPa
(309 psi).
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Improper mechanical timing
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Improper valve gap
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Broken or weak valve springs
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Worn camshaft lobes
Additional Checks
•
Inspect the generator output voltage. Repair if less than 9 volts or more than 16
volts.
•
Inspect the EGR system operating correctly.
•
Inspect the engine overheat condition. Refer to the Engine Cooling section.
•
Inspect the A/C operation.
•
Inspect the torque converter clutch (TCC) operation (A/T only).
Hesitation, Sag, Stumble
Checks Action
DEFINITION:The vehicle has a momentary lack of response when pushing down on the accelerator. The condition can occur
at any vehicle speed. The condition is usually most severe when trying to make the vehicle move from a stop. If severe
enough, the condition may cause the engine to stall.
Preliminary Checks
•
Diagnostic System Check - Engine Controls.
•
Compare the vehicle with a similar unit. Ensure the vehicle has an actual problem.
•
Remove the air cleaner and check for dirt, or for air ducts being plugged or
restricted. Replace as necessary.
•
Inspect for a proper transmission shift pattern and down shift operation.
•
Inspect the fuel quality (cetane index).
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Inspect the engine oil level and quality.
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Inspect the scan tool Data List in this section.
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Inspect the engine control module (ECM) and fuel injection pump control unit (PCU)
grounds for being clean, tight, and in their proper locations.
•
Inspect the Service Bulletins for ECM software updates.
Sensor Checks
Inspect the engine control sensors for the following conditions. Refer to the scan tool
Data List in this section.
•
Use the scan tool to compare the Engine Coolant Temperature (ECT) with the Intake
Air Temperature (IAT) and Fuel Temperature (FT) 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 on the low reference circuit and signal circuit or for a
skewed sensor.
Notice: The mass air flow (MAF) sensor is heated and as a result the IAT sensor may
indicate a higher than normal intake air temperature if the ignition switch is being ON.
FT sensor is internal to the PCU and it is part of the fuel injection pump assembly.
•
Use the scan tool to compare the MAF Sensor parameter with the Desired MAF
parameter. Start the engine and warm up (allow engine coolant temperature to reach
at least 60°C [140°F]). The MAF Sensor parameter must follow the Desired MAF
parameter within 100 mg/strk. If not, inspect the air intake system, EGR system
components and contaminated, skewed or slow MAF sensor.
•
Use the scan tool to observe the Accelerator Pedal Position Accelerator Pedal
Position. Accelerator Pedal Position parameter should change linearly from 0% to
100% according to the accelerator pedal operation.