Troubleshooting — Power System (Audi A4 B7)

27. Excessive fuel consumption

1. The air cleaner filter element is dirty or blocked.

2. Insufficient tire pressure or the wrong size tires are installed.

3. The engine has mechanical damage. Check the compression pressure, if necessary, carry out the appropriate restoration repair.

4. Excessively high idle speed/maximum speed during operation.

Petrol models

5. Components of the power supply system, electrical equipment or electronic control are faulty.

6. There are leaks in the air intake tract.

7. There is damage to the exhaust system/catalytic converter.

Diesel models

8. The return fuel line is clogged. Blow through the line in the direction from the high-pressure fuel pump to the fuel tank.

9. The fuel system is leaking. Visually inspect all fuel lines (feed, return, pressure), fuel filter and high-pressure fuel pump.

28. There are fuel leaks and/or a smell of gasoline

1. There are leaks in the fuel supply lines/vent lines.

2. The fuel tank is full - refuel only until the gun switches off automatically.

3. There are leaks/evaporation from the fuel system lines and exhaust gas toxicity reduction.

29. The engine does not start

Petrol models

1. When the starter is turned on, the electric fuel pump is not activated (the characteristic sound is missing). Lightly tap the pump body to release the jammed element. Check the correct power supply to the pump (assess the serviceability of the protective fuse and the reliability of the fastening of the contact terminals of the corresponding electrical wiring).

2. The fuel pump relay is faulty.

3. The injector valves are stuck. Check the injectors and replace them if necessary. Check the power supply to the injectors by disconnecting the injector connector, connecting a diode test lamp to the wire and turning on the starter - the lamp should start blinking.

4. There is no signal from the CKP sensor or the ECT sensor. Check the condition of the corresponding electrical wiring, query the memory of the on-board diagnostics system (OBD).

5. The fuel lines are blocked.

6. The fuel filter is clogged.

7. The air intake tract is not sealed.

8. The vacuum hoses are damaged or their tightness is compromised.

9. The fuel pressure regulator is damaged - check the residual pressure.

10. The TPS sensor is damaged.

11. No power to ECM.

12. The fuel tank ventilation is clogged, the filter in the tank is clogged.

Diesel models

13. The preheating system does not work.

14. The fuel shut-off valve is damaged.

15. The fuel shut-off valve does not open. Check the shut-off valve, engine control units and anti-theft alarm system.

16. There is a malfunction in the fuel supply system:

• the fuel lines are not passable;
• the fuel filter is clogged;
• ice/wax has accumulated in the fuel filter or pipes (in cold weather);
• the fuel tank ventilation tract is clogged, or the filter in the tank is not clear.

17. The fuel injection timing is out of adjustment.

18. The injectors are damaged.

19. The fuel injection pump is faulty - try installing a new one or a known good pump.

30. Cold engine starts poorly, runs unsteadily

1. The CO content does not meet regulatory requirements - take the appropriate measurement, check the idle speed.

2. The ECT or IAT sensor is faulty.

3. The fuel pressure does not meet the required value.

4. The air intake tract is not sealed.

31. A warmed-up engine starts poorly and runs unsteadily

1. The air intake tract is leaky. Without stopping the engine while it is idling, wet the joints of the tract elements with gasoline. - if the speed stabilizes briefly, eliminate the leaky tract.

2. The fuel pump check valve is damaged.

3. There are leaks in the fuel line.

4. Excessively high fuel pressure in the fuel system.

5. EVAP system is faulty.

6. The patency of the return fuel line to the tank is impaired.

7. The injector valves are stuck. Check the injectors, replace if necessary. Check the power supply to the injectors, disconnect the injector connector, connect a diode test lamp to the wire and turn on the starter - the lamp should start blinking.

8. There is no signal from the CKP sensor or the ECT sensor. Check the condition of the corresponding electrical wiring, query the memory of the on-board diagnostics system (OBD).



9. The fuel pressure regulator is damaged - check the residual pressure.

10. The throttle position sensor (TPS) is damaged.

11. No power to ECM.

32. The engine runs intermittently

1. There is an intermittent poor quality of contact connections in the fuel pump wiring. Check the wiring of the fuel pump, air flow meter and fuel pump relay. Check the fuse and contact terminals of the fuel pump relay. Clean the contacts, replace if necessary.

2. Low-quality fuel is used, vapor locks form in the fuel lines.

3. Insufficient fuel supply volume.

4. The fuel filter is faulty.

5. The fuel pump is faulty.

6. The injectors are faulty.

7. The lambda probe is faulty or its heating does not function.

8. TPS sensor is faulty.

9. The exhaust manifold or exhaust pipe is damaged.

10. The EVAP system is not functioning properly.

11. The fuel hoses to the high-pressure fuel pump and fuel filter have become loose (diesel models).

12. The connection points of the supply and return pipelines of the high-pressure fuel pump are mixed up.

13. The injector valves are stuck. Check the injectors, replace if necessary. Check the serviceability of the power supply to the injectors - disconnect the injector connector, connect a diode test lamp to the wire and turn on the starter - the lamp should start blinking.

14. There is no signal from the CKP sensor or the ECT sensor. Check the condition of the corresponding electrical wiring, query the memory of the on-board diagnostics system (OBD).

15. The air intake tract is not sealed.



16. The vacuum lines are leaking.

17. The fuel pressure regulator is damaged - check the residual pressure.

18. No power to ECM.

33. The engine runs intermittently in transient modes and in idle mode

1. The air intake tract is leaky. Without stopping the engine while it is idling, wet the joints of the tract elements with gasoline. If the speed stabilizes briefly, eliminate the leaky areas.

2. The idle speed setting is incorrect.

3. The total load sensor is faulty or incorrectly adjusted. Check the TPS sensor.

34. Hot engine does not start

1. The CO content in the exhaust gases is out of adjustment. Check the CO content and idle speed setting.

2. Excessively high pressure in the fuel system - check the fuel pressure, replace the regulator if necessary.

3. The patency of the return pipeline between the fuel pressure regulator and the fuel tank is impaired.

4. The ECT sensor is faulty.

5. The fuel system is not sealed.

6. The air intake tract is not sealed.

35. The diesel engine runs unstably at idle and when starting to move

1. The fuel hoses to the high-pressure fuel pump and fuel filter have become loose.

2. The connection points of the supply and return fuel lines to the high-pressure fuel pump are mixed up.

36. The engine continues to run after the ignition is turned off

1. The injectors are not sealed properly.

2. The fuel shut-off valve does not work (diesel models).