3233019 - D10 ENGINE IDLE IRREGULAR

The engine is not running smoothly when idling; in particular, it does not maintain a constant, regular value as the load varies (e.g. when electrical devices are switched on, etc.)
Results of the tests
0PRELIMINARY CHECKSAll OKProblems metOperation

Preliminarily check:

  • condition of air filter
  • the condition of the air intake circuit
  • the condition of the fuel filter
Continue to Step 1 Filter element dirty or damaged Replace the filter element Op. 5548A14
Air intake circuit component damagedReplace the component (see Assembly 1048A)
Fuel filter dirty Replace the filter element Op.   1044B20 
1CHECKING WITH DIAGNOSTIC EQUIPMENTAll OKProblems metOperation
Connect the diagnostic equipment (Examiner or other instruments) to the diagnostic socket

check

  • that there are no faults in the engine management control unit
  • the plausibility of all the parameters.
Continue to Step 2 An error is detected in the control unitContinue according to the instructions for the diagnostic equipment
Lack of dialogue with the control unit Restore the connection between the engine management control unit and the diagnostic connector ( See   E5050  DIESEL ENGINES ELECTRONIC MANAGEMENT )
2LOW PRESSURE CHECKAll OKProblems metOperation
Check the fuel supply circuit, low pressure side: if necessary, use the diagnostic equipment (Examiner) to measure the pressure values Continue to Step 3 Pressure not correct: fuel filter faulty Replace the fuel filter Op.   1044B10 
Pressure not correct: electric pump faulty Replace the electric pump Op.   1040A70 
Pressure not correct: low pressure pipes faultyReplace the low pressure pipes (see Assembly 1060F)
3HIGH PRESSURE CHECKAll OKProblems metOperation
Check the fuel supply circuit, high pressure side: for example, using the diagnostic equipment (Examiner) to measure the pressure values Continue to Step 4 Pressure not correct: pressure pump faulty Replace the pressure pump Op.   1060E10 
Pressure not correct: manifold faulty Replace the manifold Op.   1060F30 
Pressure not correct: injectors faulty Replace the injectors Op.   1060F10 
4CHECK ON CYLINDER COMPRESSIONAll OKProblems metOperation
Carry out the cylinder compression test Op.   0510A10  Continue to Step 5 Compression values not correct Restore the correct cylinder compression, for example, checking the seal of the injectors Op.   1060F10  and the cylinders (see OVERHAULING ENGINE, Subassembly 1004)
5VALVE CLEARANCE CHECKAll OKProblems metOperation
Check that the valve tappet clearance is correct. Op.   1036H14  Continue to Step 6 Clearance not correct Restore the correct valve clearance. Op.   1036H18 
6CHECK ON CORRECT OPERATIONAll OKProblems metOperation
Check that the fault is no longer presentEnd of diagnosisFault persistsSearch for the fault starting from another symptom'
The engine is not running smoothly when idling; in particular, it does not maintain a constant, regular value as the load varies (e.g. when electrical devices are switched on, etc.)
Results of the tests
0PRELIMINARY CHECKSAll OKProblems metOperation

Check:

  • the condition of the air intake circuit
  • condition and correct operation of the air filter
Continue to Step 1 Fault in air intake circuitRepair the air intake circuit
Air filter blocked Replace the filter element Op.   1048A14 
1CHECKING WITH DIAGNOSTIC EQUIPMENTAll OKProblems metOperation
Connect the diagnostic equipment (Examiner or other instruments) to the diagnostic socket

Check:

  • that there are no errors in the control unit
  • plausibility of all the parameters
  • carry out active diagnosis of E.G.R. solenoid
Continue to Step 2 An error is detected in the control unitContinue following the instructions for the diagnostic equipment
unreliable parametersContinue following the instructions for the diagnostic equipment
Lack of dialogue with the control unit Restore the connection between engine management control unit and diagnostic connector See   E5050  DIESEL ENGINES ELECTRONIC MANAGEMENT
Solenoid not working Check wiring continuity See   E5050  DIESEL ENGINES ELECTRONIC MANAGEMENT
Solenoid not working Replace the solenoid valve Op.   1080C74 
2CHECK ON FUEL FILTERAll OKProblems metOperation
Check the operation of the fuel filter Continue to Step 3 Presence of water, petrol, paraffin or dirt detected Clean the tank and pipes and replace the diesel filter cartridge Op.   1044B20 
3VALVE CLEARANCE CHECKAll OKProblems metOperation
Check that the valve tappet clearance is correct. Continue to Step 4 Valve clearance not correct Adjust the tappets Op.   1036H10 
4CHECK ON CYLINDER COMPRESSIONAll OKProblems metOperation
Carry out the cylinder compression test Continue to Step 6 Cylinder compression insufficient Continue to Step 5
5CHECKING CAUSE OF INSUFFICIENT COMPRESSIONAll OKProblems metOperation
Carry out R.R. on head to check the valve seal and check the condition of the cylinders/piston rings Continue to Step 6 Insufficient valve seal Overhaul the cylinder head Op.   1016E10 
6CHECK ON CORRECT OPERATIONAll OKProblems metOperation
Check that the fault is no longer presentEnd of diagnosisFault persists: control unit faulty Replace engine management control unit Op.   1060G80  Search for the fault starting from another symptom'