Why does my Audi 80's engine make a rattling noise when idling?

I have a 2004 Audi 80 and recently I've noticed a rattling noise coming from the engine when it's idling. It goes away when I accelerate, but it's still worrying. What could be causing this and how can I fix it?

The most common cause for engine rattling when idling is a worn out or loose serpentine belt. You can try tightening it or replacing it to see if it solves the issue.

Another possible cause is a problem with the engine valve train. It's best to take your car to a mechanic for a proper diagnosis and repair.