C280 Marine and Petroleum Engines Caterpillar

Engine Misfires, Runs Rough or Is Unstable

Usage:

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

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 symptoms under other conditions can give misleading results.

Probable Causes

Active codes and logged codes
Fuel quality
Fuel system
Fuel injectors
Lubrication
Valve train
Gear train and components of the lower end
Governor

Recommended Actions

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

Show/hide table

Table 1
Troubleshooting Test Steps	Values	Results
1. Active Codes and Logged Codes A. Establish communication between Caterpillar Electronic Technician (ET) and the Electronic Control Module (ECM). B. Monitor the diagnostic codes on Cat ET. Check for active diagnostic codes. Note: Wait at least 30 seconds in order for diagnostic codes to become active.	Codes	Result: There are active codes. Repair: Troubleshoot any codes before continuing with this procedure. Verify that the repair eliminated the problem. Result: There are no active codes. Proceed to Test Step 2.
2. Fuel Quality A. Refer to Operation and Maintenance Manual for information on the proper characteristics of the fuel for the engine. If necessary, obtain a fuel analysis in order to confirm that the correct fuel is being used for the engine. Refer to Systems Operation/Testing and Adjusting, "Fuel Quality - Test" for the proper procedure. B. Cold weather adversely affects the characteristics of the fuel. Monitor the status screen on Cat ET in order to verify that the engine has exited cold mode (if applicable). Observe the reading for coolant temperature on the Cat ET.	Fuel	Result: The fuel quality is OK. Proceed to Test Step 3. Result: The fuel quality is not OK. Repair: Replace the fuel. Verify that the repair eliminated the problem.
3. Fuel System A. Inspect the fuel system. Refer to Systems Operation/Testing and Adjusting, "Fuel System" for additional information. B. Check for the proper operation of the fuel transfer pump.	Fuel	Result: The fuel system is OK. Proceed to Test Step 4. Result: The fuel system is not OK. Repair: Make the necessary repairs. Verify that the repair eliminated the problem.
4. Fuel Injectors If service has been performed on the engine fuel system recently, verify that the injector trim files are correct. Use Cat ET to check that the injector trim files are correct for the injectors that are installed on the engine. A. Perform the "Injector Solenoid Test" on Cat ET in order to determine if all of the injector solenoids are being energized by the ECM. B. Access the "Cylinder Cutout Test" in the "Diagnostic Tests" under the "Diagnostics" menu. C. Perform the "Automatic Cylinder Cutout Test" on Cat ET.	Injector Solenoid Test	Result: The test was successful. Proceed to Test Step 5. Result: The test was not successful. Repair:Diagnose the problem and then repair the problem. Reset all active codes and clear all logged codes. Verify that the repair eliminated the problem.
5. Governor A. Inspect the governor parameters.	Governor	Result: The governor parameters need adjustment. Repair: Adjust the parameters for the governor in order to maintain stability. Verify that the repair eliminated the problem. Result: The governor parameters do not need adjustment. Proceed to Test Step 6.
6. Proper Lubrication A. Check for proper lubrication of the valve components. Check for sufficient lubrication between the injector tappets and the rocker arms. B. Check for blocked oil passages. Oil passages must be clean. Clean any oil passages that are questionable. Refer to the Disassembly and Assembly for additional information. C. Inspect the engine oil filters for ferrous material. D. Obtain an S-O-S oil analysis. The analysis will contribute to a better understanding of oil contamination and the origin of the contamination.	Lubrication	Result: The oil passages are not blocked and the engine has proper lubrication. Proceed to Test Step 7. Result: The oil passages are blocked or the engine does not have proper lubrication. Repair: Make the necessary repairs Verify that the repair eliminated the problem.
7. Valve Train Components A. Check the valve lash. Refer to Troubleshooting, "Valve Lash Is Excessive". B. Check for damage to valve train components. Remove the valve cover from the suspect cylinders. Check the following items for damage: - Camshaft - Valve rotocoil - Valve springs - Camshaft followers - Rocker shaft - Bridges - Pushrods - Injectors Refer to the Disassembly and Assembly for additional information. C. Check for valves that do not move freely. Remove the cylinder head and inspect the valves. Refer to the Disassembly and Assembly for additional information.	Valve train	Result: The valve train components are not damaged. Proceed to Test Step 8. Result: The valve train components are damaged. Repair: Make the necessary repairs, Verify that the repair eliminated the problem. Verify that the repair eliminated the problem.
8. Gear Train and Components of the Lower End A. Inspect the gear train and lower end components.	Gear train	Result: The gear train or lower end components are damaged. Repair: Replace any damaged parts. Verify that the repair eliminated the problem.

If the procedure did not correct the issue, contact your Cat dealer Technical Communicator (TC). For further assistance, your TC can confer with the Dealer Solutions Network (DSN).