audi a6 quatro starts then dies

The Mass Airflow Sensor measures air entering the engine and relays this to the car’s computer so it can meter the amount of fuel delivered from the injectors. When the sensor fails, fuel delivery is impaired and often the engine dies soon after starting. A defective Idle Air control Valve produces the same result during start-up. The Fuel Pump Relay works similarly and when defective, it can't control the pump properly during the start-up process, so the engine will die immediately after it starts. Other defects that could cause an engine to die right after it starts are, a failing crankshaft or camshaft position sensor, a severe vacuum leak, a faulty ECM, or anything that impedes proper spark. Timing can also be an issue with a worn belt. It's best to have OBD codes read and follow what shows up, or you could be searching for a long time.

The Mass Airflow Sensor measures air entering the engine and relays this to the car’s computer so it can meter the amount of fuel delivered from the injectors. When the sensor fails, fuel delivery is impaired and often the engine dies soon after starting. A defective Idle Air control Valve produces the same result during start-up. The Fuel Pump Relay works similarly and when defective, it can't control the pump properly during the start-up process, so the engine will die immediately after it starts. Other defects that could cause an engine to die right after it starts are, a failing crankshaft or camshaft position sensor, a severe vacuum leak, a faulty ECM, or anything that impedes proper spark. Timing can also be an issue with a worn belt. It's best to have OBD codes read and follow what shows up, or you could be searching for a long time.

This sounds like a security system issue, this is what they do, let it start then take away the spark and it dies, it will do this over and over again. Have you tried the shut down procedure listed in the owners manual?