C4.4 and C6.6 Engines for Caterpillar Built Machines Low Power/Poor or No Response to Throttle Caterpillar

Use the electronic service tool to make sure that the FLS and FTS parameters have been correctly entered.
Use the electronic service tool to ensure that the correct mode was selected.
Use the electronic service tool to verify that the correct engine rating has been provided.
Use the electronic service tool to verify the maximum engine speed limit.
Ensure that the repairs have eliminated the performance problems.
If the repairs have not eliminated the faults proceed to "Electrical Connectors".

Electrical Connectors

Turn the start switch to the ON position.
Use the electronic service tool to verify that the intake manifold pressure is 0 ± 0.5 kPa (00 ± 0.070 psi). Check the 5 V sensor supply for the intake manifold pressure. Refer to Troubleshooting, "5 Volt Engine Pressure Sensor Supply Circuit - Test".
Use the electronic service tool to verify the throttle position status.
Run the engine until the speed is equal to the maximum no-load speed.
Use the electronic service tool to make sure that the throttle is set to reach the maximum no-load speed.
If the maximum no-load speed can not be obtained refer to Troubleshooting, "Throttle Switch Circuit - Test".
If the fault has not been eliminated, proceed to "Air Intake and Exhaust System".

Air Intake and Exhaust System

Ensure that the air filter is clean and serviceable.
Check the air intake and the exhaust system for the following defects:
- Blockages
- Restrictions
- Damage to the air intake and exhaust lines and hoses
Make all necessary repairs to the engine.
If the fault has not been eliminated, proceed to "Valve Lash".

Valve Lash

Check the valve lash and reset the valve lash, if necessary. Refer to Systems Operation, Testing and Adjusting, "Engine Valve lash - Inspect and Adjust".
If the repair does not eliminate the fault proceed to "Turbocharger".

Note: The turbocharger that is installed on this engine is a nonserviceable item. If any mechanical fault exists, except for the wastegate actuator, then the turbocharger must be replaced. The wastegate actuator can be replaced.

Ensure that the mounting bolts for the turbocharger are tight.
Check that the oil drain for the turbocharger is not blocked or restricted.
Check that the compressor housing for the turbocharger is free of dirt and debris.
Check that the turbine housing for the turbocharger is free of dirt and debris.
Check that the turbine blades rotate freely in the turbocharger.
Ensure that the wastegate on the turbocharger is adjusted correctly. Refer to Systems Operation, Testing and Adjusting, "Wastegate - Inspect". If the wastegate actuator is faulty, replace the wastegate actuator. Refer to Disassembly and Assembly, "Turbocharger - Disassemble" and Disassembly and Assembly, "Turbocharger - Assemble".
If necessary, replace the turbocharger. Refer to Disassembly and Assembly, "Turbocharger - Remove" and Disassembly and Assembly, "Turbocharger - Install".
Check that the repairs have eliminated the faults.
If the fault has not been eliminated, proceed to "Fuel Supply".

Fuel Supply

Visually check the fuel tank for fuel. The fuel gauge may be faulty.
Ensure that the fuel supply valve (if equipped) is in the full OPEN position.
If the temperature is below 0 °C (32 °F), check for solidified fuel (wax).
Check the primary filter/water separator for water in the fuel.
Check for fuel supply lines that are restricted.
Check that the low pressure fuel lines are tight and secured properly.
Check the fuel filters.
Check the diesel fuel for contamination. Refer to Systems Operation, Testing and Adjusting, "Fuel Quality - Test".
Check for air in the fuel system. Refer to Systems Operation, Testing and Adjusting, "Air in Fuel - Test".
Ensure that the fuel system has been primed. Refer to Systems Operation, Testing and Adjusting, "Fuel System - Prime".
Check the fuel pressure. Refer to Systems Operation, Testing and Adjusting, "Fuel System Pressure - Test".
If the repair does not eliminate the fault refer to "Low Compression (Cylinder Pressure)".

Low Compression (Cylinder Pressure)

Perform a compression test. Refer to Systems Operation, Testing and Adjusting, "Compression - Test ".
If low compression is noted on any cylinders, investigate the cause and rectify any faults.
Possible causes of low compression are shown in the following list:
- Loose glow plugs
- Faulty piston
- Faulty piston rings
- Worn cylinder bores
- Worn valves
- Faulty cylinder head gasket
- Damaged cylinder head
Perform all necessary repairs.
Ensure that the repairs have eliminated the faults.
If the repair does not eliminate the fault refer to "Individual Malfunctioning Cylinders".

Individual Malfunctioning Cylinders

Use the electronic service tool to perform the "Cylinder Cut-out Test". Note if there is any reduction in engine speed. If a reduction in engine speed is not noted, the isolated cylinder is not operating under normal conditions. If the isolation of a particular cylinder results in a reduction of engine speed that is less than normal, this may indicate that the cylinder is operating below normal performance. Investigate the cause of the fault on any cylinder that is not operating. Investigate the cause of the fault on any cylinder that is operating below normal performance.
If all cylinders have been checked and no faults were detected proceed to "Electronic Unit Injectors".

Electronic Unit Injectors

Use the electronic service tool to perform the "Cylinder Cut-out Test". Note if there is any reduction in engine speed. If a reduction in engine speed is not noted, the isolated electronic unit injector is not operating under normal conditions. If the isolation of a particular cylinder results in a reduction of engine speed that is less than normal, this may indicate that the electronic unit injector is operating below normal performance.
Remove the electronic unit injector from the suspect cylinder. Refer to Disassembly and Assembly, "Electronic Unit Injector - Remove".
Install a new electronic unit injector. Refer to Disassembly and Assembly, "Electronic Unit Injector - Install".
Repeat the test in 1. If the fault is still apparent, remove the replacement electronic unit injector and install the original electronic unit injector. Refer to Disassembly and Assembly, "Electronic Unit Injector - Remove" and Disassembly and Assembly, "Electronic Unit Injector - Install".
If the fault is not eliminated, check for active diagnostic fault codes.