Why does my Audi A2 engine make a loud knocking sound when I start it?

I recently purchased an Audi A2 and have noticed that when I start the engine, it makes a loud knocking sound for a few seconds before quieting down. Is this normal or should I be concerned?

Based on your description, it is likely that your engine is experiencing a phenomenon known as engine knock. This occurs when the air/fuel mixture in the combustion chamber ignites too early, causing a knocking or pinging sound. It is important to address this issue as it can lead to engine damage over time.

One possible cause of engine knock in Audis is low quality fuel. Make sure you are using high quality gasoline and consider using a fuel additive to help clean deposits from your engine. You may also want to have your spark plugs and ignition system checked.

If the loud knocking sound is accompanied by poor performance and/or a decrease in fuel efficiency, it is possible that you have a faulty engine component such as a worn out piston or connecting rod. It is best to have a mechanic inspect your engine to pinpoint the exact cause.