Engine stalling Audi A6

When an Audi A6 C7 experiences engine stalling, it can be due to a variety of issues ranging from fuel delivery problems to electronic system faults. Here is a detailed step-by-step guide to diagnose and repair this issue.

Step 1: Retrieve Diagnostic Trouble Codes (DTCs)

1. Tools Required: OBD-II Scanner
2. Procedure:
   • Connect the OBD-II scanner to the vehicle’s diagnostic port, typically located under the dashboard on the driver's side.
   • Turn the ignition to the "ON" position without starting the engine.
   • Use the scanner to read any stored DTCs. Note these codes, as they will guide further diagnosis.

Step 2: Check Fuel Delivery System

1. Tools Required: Fuel pressure gauge, multimeter
2. Procedure:
   • Fuel Pressure Test:
     • Locate the fuel rail and attach the fuel pressure gauge to the schrader valve.
     • Start the engine and observe the fuel pressure. Compare it to the manufacturer’s specifications (usually around 50-60 psi for this model).
     • If the pressure is low, inspect the fuel pump, fuel filter, and fuel lines for clogs or leaks.
   • Fuel Pump Relay and Fuse:
     • Check the fuel pump relay and fuse in the fuse box. Replace if faulty.

Step 3: Inspect Air Intake System

1. Tools Required: Visual inspection, multimeter
2. Procedure:
   • Ensure the air intake duct and air filter are not clogged or damaged.
   • Inspect the Mass Air Flow (MAF) sensor for contamination or damage. Clean with a MAF cleaner if dirty.

Step 4: Examine the Ignition System

1. Tools Required: Spark tester, multimeter
2. Procedure:
   • Check the spark plugs for wear or fouling. Replace if necessary.
   • Test the ignition coils for proper operation using a spark tester or scan for misfire codes.

Step 5: Check for Vacuum Leaks

1. Tools Required: Smoke machine or carb cleaner
2. Procedure:
   • Use a smoke machine to introduce smoke into the intake system and identify any leaks.
   • Alternatively, spray carb cleaner around suspect areas (intake manifold gasket, vacuum hoses) and listen for changes in engine RPM.

Step 6: Evaluate the Electronic Throttle Control (ETC) System

1. Tools Required: Diagnostic scanner, multimeter
2. Procedure:
   • Use the scanner to perform an Electronic Throttle Control (ETC) test.
   • Inspect the throttle body for carbon build-up and clean if necessary.

Step 7: Inspect Engine Sensors

1. Tools Required: Multimeter, scan tool
2. Procedure:
   • Check the Crankshaft Position Sensor and Camshaft Position Sensor for proper operation.
   • Test with a multimeter or scan tool.

Repair Instructions

Fuel System Repairs

• Replace the fuel filter if clogged.
• Replace a faulty fuel pump after verifying low or no pressure.

Air and Ignition System Repairs

• Replace the air filter if dirty or clogged.
• Clean or replace the MAF sensor and throttle body.
• Replace worn or fouled spark plugs and faulty ignition coils.

Vacuum Leak Repairs

• Replace any cracked or leaking vacuum hoses.
• Replace intake manifold gaskets if leaking.

Sensor and Electronic System Repairs

• Replace faulty sensors (Crankshaft Position Sensor, Camshaft Position Sensor) as needed.
• Recalibrate or replace the throttle body if defective.

Final Steps

• Clear all DTCs using the OBD-II scanner.
• Test drive the vehicle to ensure that the issue is resolved and no new DTCs appear.

By following these detailed steps, you can effectively diagnose and repair the engine stalling issue on an Audi A6 C7. If the problem persists after performing these checks and repairs, it may be necessary to consult a professional technician or consider the possibility of more complex issues such as ECU or wiring problems.