C4.4 and C6.6 Engines Caterpillar

Engine Misfires, Runs Rough or Is Unstable

Usage:

C4.4 448

Note: If the fault is intermittent and the fault cannot be duplicated, refer to Troubleshooting, "Power Is Intermittently Low or Power Cutout Is Intermittent".

Note: If the fault 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 symptoms under other conditions can give misleading results.

Probable Causes

Diagnostic codes
Fuel supply
Transfer Pump Inlet Regulator (TPIR)
Electric Fuel Lift Pump (EFLP)
Return fuel lines
Throttle position sensor
CAN data link
High-pressure fuel pump
Low compression (cylinder pressure)
Electronic unit injectors
Individual malfunctioning cylinder

Recommended Actions

Note: The procedures have been listed in order of probability. Complete the procedures in order.

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Table 1
Troubleshooting Test Steps	Values	Results
1. Diagnostic Codes A. Establish communication between the electronic service tool and the Electronic Control Module (ECM). Refer to Troubleshooting, "Electronic Service Tools", if necessary. B. Download the Warranty Report and the Product Status Report with Histograms before performing any troubleshooting or clearing any diagnostic codes. Note: The downloaded information will be required by the Dealer Solutions Network (DSN) if troubleshooting assistance is needed. C. Use the electronic service tool to check for active or logged codes.	Codes	Result: There are active codes. Repair: Troubleshoot any active codes before continuing with this procedure. Result: There are no active codes. Proceed to Test Step 2.
2. Fuel Supply A. Visually check the fuel tank for fuel. The fuel gauge may be faulty. B. Ensure that the vent in the fuel cap is not filled with debris. C. Ensure that the fuel supply valve (if equipped) is in the full OPEN position. D. Check the primary filter/water separator for water in the fuel. E. Check for fuel supply lines that are restricted. F. Check that the Electric Fuel Lift Pump (EFLP) is operating. If the EFLP is suspect, refer to Troubleshooting, "Relay - Test (Electric Fuel Lift Pump)". G. Check for air in the fuel system. Refer to Systems Operation, Testing, and Adjusting, "Air in Fuel - Test". H. Obtain a fuel analysis to confirm that the correct fuel is being used. Refer to Systems Operation/Testing and Adjusting, "Fuel Quality - Test" for the correct procedure.	Fuel supply	Result: There is air in the fuel system. Repair: Prime the fuel system. Refer to Systems Operation, Testing, and Adjusting, "Fuel System - Prime". Result: The fuel quality is not OK. Repair: Replace the fuel. Replace the in line fuel filter that is upstream of the EFLP. Replace the primary and secondary fuel filters. Verify that the repair eliminated the fault. Proceed to Test Step 13. Result: The fuel quality is OK. Proceed to Test Step 3.

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Illustration 1	g03700009
Transfer Pump Inlet Regulator (TPIR) components on a C4.4 engine (1) Transfer Pump Inlet Regulator (TPIR) (2) TPIR return port

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Illustration 2	g06100802
Transfer Pump Inlet Regulator (TPIR) components on a C6.6 engine (1) Transfer Pump Inlet Regulator (TPIR) (2) TPIR return port

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Illustration 3	g02485896
Minimum TPIR flow rate in a 12 VDC system on a C4.4 engine

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Illustration 4	g02485897
Minimum TPIR flow rate in a 24 VDC system on a C4.4 engine

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Illustration 5	g02355128
Minimum TPIR flow rate in a 12 VDC system on a C6.6 engine

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Illustration 6	g02355130
Minimum TPIR flow rate in a 24 VDC system on a C6.6 engine

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Table 2
Troubleshooting Test Steps	Values	Results
3. Transfer Pump Inlet Regulator (TPIR) Flow Test For a C4.4 engine, refer to Illustration 1. For a C6.6 engine, refer to Illustration 2. A. Disconnect the TPIR return line from the drain port on the TPIR. Install a suitable blanking cap on the open port in the TPIR return line. B. Connect a temporary drain line to the drain port on the TPIR. C. Place the end of the temporary drain line into a suitable calibrated container. D. With the isolator switch in the ON position but the engine not running, use a suitable multimeter to measure the input voltage to the EFLP. Record the reading. E. With the isolator switch in the ON position but the engine not running, measure the fuel flow from the temporary drain line. F. Refer to Illustration 3 through 6 for the minimum acceptable flow rate. G. Remove the temporary drain line from the drain port on the TPIR. Connect the TPIR return line to the TPIR.	TPIR flow rate	Result: The fuel flow is greater than the minimum limit. Proceed to Test Step 5. Result: The fuel flow is less than the minimum limit. Proceed to Test Step 4.

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Illustration 7	g02527498
Minimum EFLP flow rate in a 12 VDC system

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Illustration 8	g02527518
Minimum EFLP flow rate in a 24 VDC system

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Table 3
Troubleshooting Test Steps	Values	Results
4. EFLP Flow Test at the Primary Fuel Filter Inlet A. Make sure the keyswitch is in the OFF position. B. Disconnect the fuel inlet connection from the primary fuel filter head. C. Install a suitable blank on the fuel inlet port on the primary fuel filter head. D. Place the open end of the fuel inlet line in a suitable calibrated container. E. With the keyswitch in the ON position, measure the input voltage at the EFLP. Record the result. F. With the keyswitch in the ON position, measure the flow from the fuel inlet line. Record the result. G. Check the recorded voltage and fuel flow on the graph in Illustration 7 or 8.	EFLP flow	Result: The fuel flow is below the minimum value for the recorded voltage. Repair: Replace the EFLP. Refer to Disassembly and Assembly, "Fuel Priming Pump - Remove and Install". Result: The fuel flow is above the minimum value for the recorded voltage. Proceed to Test Step 5.
5. Check the Return Fuel Lines A. Make sure that the TPIR return line is not blocked or kinked. B. If the TPIR return line is clear, confirm that the Electric Fuel Lift Pump (EFLP) is operating. Make sure that fuel lines between the EFLP and the TPIR are not blocked or kinked.	Return lines	Result: The TPIR return line or the fuel lines between the EFLP and the TPIR are blocked or kinked. Repair: Clear or replace the blocked line. Proceed to Test Step 13. Result: The TPIR return line and the fuel lines between the EFLP and the TPIR are clear. Repair: Replace the EFLP. If the fault is still present, proceed to Test Step 6. If the fault is eliminated, proceed to Test Step 13.
6. Throttle Signal A. Use the electronic service tool and observe the signal for the throttle. Make sure that the throttle response is smooth and progressive.	Throttle	Result: The throttle signal is erratic. Repair: Refer to the appropriate circuit test for the type of throttle that is installed. Proceed to Test Step 13. Result: The throttle response is OK. Proceed to Test Step 7.
7. Check the CAN Data Link Note: The requested engine speed signal is sent to the engine ECM through the CAN data link. A. Use the electronic service tool to check for diagnostic codes that are related to the CAN data link.	Throttle	Result: The CAN data link is suspect. Repair: Test the CAN data link. Refer to Troubleshooting, "CAN Data Link - Test". Proceed to Test Step 13. Result: The CAN data link is OK. Proceed to Test Step 8.
8. High-Pressure Fuel Pump SCV A. Use the electronic service tool to perform a solenoid test on the fuel injection pump. Refer to Troubleshooting, "Solenoid Valve - Test".	HP fuel pump	Result: The solenoid valve test fails. Repair: Replace the HP fuel pump SCV and solenoid assembly. Proceed to Test Step 13. Result: The solenoid valve test passes successfully. Proceed to Test Step 9.
9. High-Pressure Fuel Pump Note: The fuel injection pump that is installed by the factory is a nonserviceable item. If any fault occurs within the fuel injection pump, the fuel injection pump must be replaced. A. Use the electronic service tool to select the correct screen to display any diagnostic trouble codes that relate to the fuel injection pump.	HP fuel pump	Result: There are diagnostic codes associated with the high-pressure fuel pump. Repair: Diagnose the codes. Refer to Troubleshooting, "Troubleshooting with a Diagnostic Code". If necessary, replace the high-pressure fuel pump. Proceed to Test Step 13. Result: The high-pressure fuel pump is OK. Proceed to Test Step 10.
10. Low Compression (Cylinder Pressure) A. Perform a compression test. Refer to Systems Operation, Testing, and Adjusting, "Compression - Test".	Cylinder compression	Result: The results of the compression test are outside the specifications. Repair: Investigate the cause and rectify any faults. Note: 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 Proceed to Test Step 13. Result: The results of the compression test are OK. Proceed to Test Step 11.
11. Electronic Unit Injectors A. Use the electronic service tool to perform the automatic "Cylinder Cut Out Test". Note: If the compression test that was performed in Test Step 9 was satisfactory, the "Cylinder Cut Out Test" will identify any faulty injectors.	Electronic Unit Injectors	Result: A faulty injector is indicated. Repair: Remove any faulty electronic unit injectors. Refer to Disassembly and Assembly, "Electronic Unit Injector - Remove". Install new electronic unit injectors. Refer to Disassembly and Assembly, "Electronic Unit Injector - Install". Repeat the automatic "Cylinder Cut Out Test". 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". Proceed to Test Step 13. Result: All injectors are OK. Proceed to Test Step 12.
12. Individual Malfunctioning Cylinders A. With the engine speed at a fast idle, use the electronic service tool to perform the manual "Cylinder Cut Out Test". As each cylinder is cut out, listen for a change in the sound from the engine. When a cylinder is cut out, there should be a noticeable change in the sound of the engine. If a change in the sound of the engine is not noted, the isolated cylinder is not operating under normal conditions. If the isolation of a cylinder results in a change in the sound that is less noticeable, the cylinder may be operating below normal performance.	Cylinders	Result: The test indicates a faulty cylinder. Repair: 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. Proceed to Test Step 13. Result: The test indicates that all cylinders are OK. Contact the Dealer Solutions Network (DSN).
13. Check the Aftertreatment System for Oil or Fuel A. Remove excess oil or fuel from the piping with a clean cloth. B. Remove the Clean Emissions Module (CEM). Refer to Disassembly and Assembly, "Clean Emissions Module - Remove and Install". C. Support the CEM over a suitable container with the exhaust inlet downwards. Leave the CEM to drain for 8 hours. D. Check the quantity of drained oil or fuel in the container.	CEM	Result The volume of drained oil or fuel is greater than 1.0 L (1.05669 qt). Repair: Install a replacement CEM. Refer to Disassembly and Assembly, "Clean Emissions Module - Remove and Install". Return the unit to service. Result The volume of drained oil or fuel is less than 1.0 L (1.05669 qt). Proceed to Test Step 14.
14. Recover the Aftertreatment System A. Clean any remaining oil or fuel from the piping and the CEM inlet with a clean cloth. B. Install the Clean Emissions Module (CEM). Refer to Disassembly and Assembly, "Clean Emissions Module - Remove and Install". C. Run the engine at high idle with no load for a minimum of 20 minutes. D. Use the electronic service tool to perform the "Aftertreatment Recovery Procedure". While the procedure is progressing, check for smoke from the exhaust. Some smoke will be evident during the procedure. The smoke must dissipate before the procedure is completed.	CEM	Result: The "Aftertreatment Recovery Procedure" completes with a soot load of less than 80% and no smoke from the exhaust. Return the unit to service. Result The "Aftertreatment Recovery Procedure" completes with a soot load of more than 80% or smoke from the exhaust. Contact the Dealer Solutions Network (DSN).