Surges - Isuzu N 2008 Series Workshop Manual

1A-332 Engine Control System (4JJ1)

Surges

Checks
Difinition:
The engine has a power variation under a steady throttle or cruise. The vehicle seems to speed up and slow down with no
change in the accelerator pedal.
Preliminary Checks
Sensor Checks
Fuel System Checks
• Diagnostic System Check - Engine Controls.
• Ensure the driver understands the A/C compressor operation.
• Use the scan tool in order to make sure the Vehicle Speed parameter reading
matches the vehicle speedometer.
• Inspect the ECM grounds for being clean, tight, and in their proper locations.
• Inspect that the harness connectors are correctly connected.
• Inspect the fuel type and quality.
• Inspect the programmed fuel injector ID code for each cylinder.
• Inspect the Scan Tool Data List in this section.
• Inspect the Service Bulletin.
Inspect the engine control sensors for the following conditions. Refer to Scan Tool Data
List in this section.
• Observe the Mass Air Flow (MAF) parameter for a skewed or slow MAF sensor.
• 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.
• Observe the Accelerator Pedal Position (APP). APP parameter should change
linearly from 0 to 100% according to the accelerator pedal operation.
Inspect the fuel system for the following conditions. Refer to Fuel System Check chart
and appropriate procedure in Section 1D Engine Fuel.
• Air in the fuel system.
• Water contamination in the fuel.
• Fuel waxing or icing.
• Fuel filter clogging.
• Fuel leak off from the fuel pressure limiter valve and fuel injectors.
• Fuel lines between the fuel tank and fuel supply pump for being crushed, kinked,
tightness, cracks and plugged.
• A plugged fuel tank vent hose.
• Inside the fuel tank for any foreign material that may be getting drawn into the fuel
line pickup causing a blocked condition.
• Fuel supply pump operation.
Notice: The fuel supply pump must be timed to the engine and adjustment value must
be learned to the ECM.
• Perform the Cylinder Balance Test with a scan tool.
• Perform the Injector Forced Drive with a scan tool.
Action