D05 ENGINE DOES NOT PRODUCE BEST PERFORMANCE - Alfa - 156 - eLearn

3233018 - D05 ENGINE DOES NOT PRODUCE BEST PERFORMANCE

The engine runs smoothly at medium-low speeds, but does not reach iits usual maximum performance (both in terms of speed and acceleration)

0	PRELIMINARY CHECKS	All OK	Problems met	Operation
		Results of the tests
	Preliminarily check: the condition of the air intake circuit the condition of the fuel filter for a possible obstruction of the exhaust pipes for any obstacles to the complete accelerator pedal travel	Continue to Step 1	Air intake circuit component damaged	Replace the component (see Assembly 1048A)
			Filter dirty	Replace the filter element Op. 1044B20
			Exhausts obstructed	Replace the component involved (see Assembly 1076B)
1	CHECKING WITH DIAGNOSTIC EQUIPMENT	All OK	Problems met	Operation
	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 unit	Continue according to the instructions for the diagnostic equipment
		Continue to Step 2	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 ).
2	ACCELERATOR CHECK	All OK	Problems met	Operation
	Check that the accelerator pedal potentiometer is correctly calibrated	Continue to Step 3	Potentiometer setting incorrect	Restore the operation of the potentiometer
3	CHECK ON TURBOCHARGER	All OK	Problems met	Operation
	Check that the turbocharger is working properly	Continue to Step 4	Turbocharger faulty	Renew the turbocharger Op. 1064A10
4	CHECK ON BRAKE PEDAL SWITCH	All OK	Problems met	Operation
	Check that the brake switch is working properly (for example, check that the brake lights are working properly)	Continue to Step 5	Brake pedal switch connection faulty	Renew the connection between the switch and the engine management control unit ( See E5050 DIESEL ENGINES ELECTRONIC MANAGEMENT )
		Continue to Step 5	Brake pedal switch faulty	Replace the brake pedal switch Op. 5550D10
5	CHECK ON CORRECT OPERATION	All OK	Problems met	Operation
	Check that the fault is no longer present	End of diagnosis	Fault persists	Search for the fault starting from another symptom'

The engine runs smoothly at medium-low speeds, but does not reach iits usual maximum performance (both in terms of speed and acceleration)

Results of the tests

PRELIMINARY CHECKS

All OK

Problems met

Operation

Check, in order:

the condition of the air intake circuit
no faults in the air filter;
seal of the diesel pipes;
accelerator pedal travel;
absence of obstructions in the catalytic converter

Continue to Step 1

Fault in air intake circuit

Repair the air intake circuit

Air filter blocked

Replace the filter element Op. 1048A14

Leaks from the diesel pipes

stop the leak

Accelerator pedal travel incomplete

Eliminate the cause of the problem

Catalyzer obstructed

Replace the catalyzer

Operation incorrect

Carry out the actuator leak test See Test 1064BC Variable geometry turbocharger actuator leakage test

CHECK TURBOCHARGER ADJUSTMENT

All OK

Problems met

Operation

With the diagnostic equipment, carry out active diagnosis on the turbocharger regulating solenoid check the operation of the variable geometry control actuator See Test 1064BC Variable geometry turbocharger actuator leakage test

Continue to Step 2

Solenoid not working

Check the continuity of the wiring See E5050 DIESEL ENGINES ELECTRONIC MANAGEMENT and if necessary replace the solenoid

Actuator does not work correctly

Check the condition of the vacuum circuit, and if necessary replace the damaged components

CHECKING WITH DIAGNOSTIC EQUIPMENT

All OK

Problems met

Operation

Connect the diagnostic equipment (Examiner or other instruments) to the diagnostic socket

check

for errors in the control unit
plausibility of parameters;
carry out active diagnosis of E.G.R. solenoid

Continue to Step 3

An error is detected in the control unit

Continue following the instructions for the diagnostic equipment

unreliable parameters

Continue following the instructions for the diagnostic equipment.

E.G.R. solenoid not working

Check wiring continuity See E5050 DIESEL ENGINES ELECTRONIC MANAGEMENT

E.G.R. solenoid not working

Replace the solenoid valve Op. 1080C74

ROAD TEST WITH DIAGNOSTIC EQUIPMENT

All OK

Problems met

Operation

Road test the vehicle keeping the diagnostic instrument connected.

Make sure that the conditions in which the problem occurs are reproduced

check

for errors in the control unit
plausibility of all the parameters

Continue to Step 4

Errors suddenly occur in the control unit

Continue following the instructions for the diagnostic equipment

Parameters off scale

Continue 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

CHECK ON BRAKE PEDAL SWITCH

All OK

Problems met

Operation

Check that the brake pedal switch is working properly

Continue to Step 5

Brake pedal does not return

Eliminate the cause of the sticking

Switch stuck in closed position

Replace the switch Op. 1060G38

Wiring short circuited

Eliminate the cause of the problem

CHECK ON TURBOCHARGER

All OK

Problems met

Operation

Check as described in test 1064BA the operation of the turbocharger

Continue to Step 6

Turbocharger faulty

Replace the turbocharger Op. 1064A10

HIGH PRESSURE CHECK

All OK

Problems met

Operation

Connect the diagnostic equipment (Examiner or other instruments) to the diagnostic socket Check that the diesel pressure parameter is correct See Test 1060D Check high pressure fuel circuit

Continue to Step 14

Pressure not correct

Continue to Step 7

CHECK ON RETURN LOW PRESSURE

All OK

Problems met

Operation

Check that the pressure in the fuel return pipe to the tank is less than 1 bar See Test 1060A Check low pressure fuel circuit

Continue to Step 8

Pressure above maximum limit: return pipe to tank (front section) blocked)

Repair the pipe (front section); if necessary replace it Op. 1040B54

Pressure above maximum limit: return pipe to tank (rear section) blocked

Repair the pipe (rear section); if necessary replace it Op. 1040B56

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