3176C, 3406E and 3456 Industrial Engines Troubleshooting – Acceleration Is Poor or Throttle Response Is Poor

Probable Causes


  • Fuel supply 
  • Engine derate or active codes 
  • Cold mode 
  • Parameters 
  • Flash file 
  • Throttle signal 
  • Electrical connectors 
  • Unit injectors 
  • “Turbocharger outlet (boost) pressure sensor” 
  • Air inlet and exhaust system 

Recommended Actions

Note: If the problem only occurs under certain conditions, test the engine under those conditions. Examples of certain conditions are high engine speed, full load and engine operating temperature. Troubleshooting the symptoms under other conditions can give misleading results.

Fuel Supply


  1. Visually check the fuel level in the fuel tank. Do not rely on the fuel gauge only. If necessary, add fuel to the fuel tank. If the engine has been run out of fuel, it will be necessary to prime the fuel system. Refer to Operation and Maintenance Manual for the correct procedure.


  1. Check the fuel lines for the following problems: restrictions, collapsed lines and pinched lines. If problems are found with the fuel lines, repair the lines and/or replace the lines.


  1. Check the fuel tank for debris or foreign objects which may block the fuel supply.


Do not crank the engine continuously for more than 30 seconds. Allow the starting motor to cool for two minutes before cranking the engine again.


  1. Prime the fuel system if any of the following procedures have been performed: 
    • Replacement of the fuel filters 
    • Service on the low pressure fuel supply circuit 
    • Replacement of unit injectors 

    Note: Check the fuel system for air. Refer to Systems Operation/Testing and Adjusting for information that is related to checking the fuel system for air.


  1. Check fuel quality. Cold weather adversely affects the characteristics of the fuel. Refer to the engine’s Operation and Maintenance Manual for information on improving the characteristics of the fuel during cold weather operation.


  1. Check the filtered fuel pressure while the engine is being cranked. Refer to Systems Operation/Testing and Adjusting for the test procedure and for the correct pressure values.If the fuel pressure is low, replace the fuel filters. Clean the primary filter/water separator of debris. Refer to the Operation and Maintenance Manual for details.

    If the fuel pressure is still low, check the operation of the fuel pressure regulating valve. Also, check for the proper operation of the fuel transfer pump. Refer to Systems Operation/Testing and Adjusting for test information.

Engine Derate or Active Codes

Some engine monitoring parameters that are capable of triggering an engine derate do not produce an event code. Connect Caterpillar Electronic Technician (ET) in order to check for a derate of the engine.

Certain diagnostic codes and/or event codes may cause poor performance. Use Cat ET to check for active codes and for logged codes. Troubleshoot any codes that are present before continuing with this procedure.

Note: Although a sensor’s signal may be in the operational range of the sensor, the signal may not represent the actual reading. Use Cat ET to check that the pressures and the temperatures are fluctuating. Also check that the values are reasonable for the conditions that are present.

Cold Mode

The Electronic Control Module (ECM) limits engine power during cold mode operation. The ECM may modify the injection timing and the ECM may cut out certain engine cylinders. This will increase startability and this will reduce warm up time. Cold mode is activated whenever the engine coolant temperature falls below a predetermined value. Cold mode remains active until the engine has warmed or a time limit is exceeded.


Verify that the correct parameters are being used.

Flash File

Verify that the latest flash file is installed in the ECM.

Throttle Signal

Monitor the status for “Throttle Position” on Cat ET. Verify that the status for “Throttle Position” is stable and that the engine is able to reach high idle speed. If a problem is suspected with the throttle, refer to Troubleshooting, “Speed Control – Test”.

Electrical Connectors

Check for correct installation of the J1/P1 and J2/P2 ECM connectors and the connectors for the unit injectors. Refer to Troubleshooting, “Electrical Connectors – Inspect”.

Unit Injectors


  1. Perform the “Injector Solenoid Test” on Cat ET in order to determine if all of the injector solenoids are being energized by the ECM.


  1. Perform the “Cylinder Cutout Test” on Cat ET in order to determine the performance of each cylinder. Refer to Troubleshooting, “Injector Solenoid – Test” for the proper procedure.

“Turbocharger Outlet (Boost) Pressure Sensor”


  1. Monitor the status of “Fuel Position”, “Rated Fuel Limit”, and “FRC Fuel Limit” on Cat ET while the engine is operating under full load. These parameters should agree with the following:
    Table 1
    “Fuel Position” = “Rated Fuel Limit”
    “Fuel Position” < “FRC Fuel Limit”

    If “Fuel Position” equals “Rated Fuel Limit” and “Fuel Position” is less than “FRC Fuel Limit”, the electronics are operating correctly.


  1. Monitor the status of “Turbocharger Outlet (Boost) Pressure” and “Atmospheric Pressure” for normal operation on Cat ET. When the engine is not running, “Turbocharger Outlet (Boost) Pressure” should be 0 kPa (0 psi).

Air Inlet and Exhaust System


  1. Observe the check engine lamp. Check for an air filter restriction indicator. Clean plugged air filters or replace plugged air filters. Refer to the Operation and Maintenance Manual.


  1. Check the air inlet and exhaust system for restrictions and/or leaks. Refer to Systems Operation/Testing and Adjusting for information on inspecting the air inlet and exhaust system.

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