If the problem is intermittent and the problem cannot be duplicated, refer to Troubleshooting, "Power Is Intermittently Low or Power Cutout Is Intermittent".
If the engine speed is unstable and the problem only occurs during idle, there may be a problem with the circuit for the fast idle switch. Refer to Troubleshooting, "Speed Control (Auxiliary) - Test".
- Fuel supply
- Problem with the P2 connector
- Problem with a unit injector connector
- Malfunctioning injector
- Accelerator pedal position sensor
- Power train data link
- Engine Control Module (ECM)
- Valve lash
Note: If the problem only occurs under certain conditions, test the engine under those conditions. Examples of certain conditions are high rpm, full load and engine operating temperature. Troubleshooting the problem under other conditions can give misleading results.
Check the fuel quality. For further information, refer to the engine's Operation and Maintenance Manual.
Check the fuel pressure. Refer to Systems Operation/Testing and Adjusting, "Fuel System".
Ensure that the fuel system has been primed. Refer to the engine's Operation and Maintenance Manual for the correct procedure.
Check for fuel supply lines that are restricted.
Check the fuel filters.
Cold weather adversely affects the characteristics of the fuel. Refer to the Operation and Maintenance Manual for information on improving the characteristics of the fuel during cold weather operation.
Check for air in the fuel system. Refer to Systems Operation/Testing and Adjusting, "Fuel System".
Check the P2 Electrical Connector
Verify that the J2/P2 connectors are fully connected, free of moisture, and free of corrosion.
Check the Connectors for the Unit Injectors
Verify that each unit injector connector is fully connected, free of moisture, and free of corrosion.
Check for a Malfunctioning Injector
Access the "Cylinder Cutout Test" on the Caterpillar Electronic Technician (ET). Disable each injector one at a time. If a malfunctioning injector can be identified, refer to Troubleshooting, "Injector Solenoid - Test".
Check the Accelerator Pedal Position Sensor
If the engine is in the cruise control mode and the problem does not occur, check the accelerator pedal position sensor.
Use the "Cruise/Idle On/Off Switch" to put the engine in idle mode. Vary the engine rpm with the set/resume switches.
If both of the following conditions are met, connect Cat ET and monitor the status of the accelerator pedal position sensor.
- The engine is stable by using idle mode to control the engine rpm.
- The engine is unstable by using the accelerator pedal position sensor.
If the status of the accelerator pedal position sensor is unstable, refer to Troubleshooting, "Sensor Signal (PWM) - Test".
Check the Systems on the Power Train Data Link
A system that is connected to the power train data link may be affecting the engine's power. These systems include the brakes and the transmission. Monitor the appropriate parameters on Cat ET while the vehicle is experiencing problems. Determine if the systems are limiting the engine's speed.
Determine if the condition is normal operation. Refer to the vehicle's Original Equipment Manufacturer (OEM) if the condition is not normal operation.
The ECM may be operating incorrectly. Temporarily connect a test ECM. Refer to Troubleshooting, "ECM - Replace". If the engine starts with the test ECM, connect the original ECM and verify that the problem returns. If the problem returns with the original ECM, replace the original ECM.
Refer to Systems Operation/Testing and Adjusting, "Engine Valve Lash - Inspect/Adjust" for the correct procedure.