Why does my Audi A2 engine make a rattling noise when idling?

I've recently noticed a loud rattling noise coming from my Audi A2's engine when the car is idle. The noise seems to disappear when I start driving. Does anyone know what could be causing this and how I can fix it?

Based on my experience with my own Audi A2, this could be a sign of a failing timing chain tensioner. It's a common issue with these engines and should be fixed as soon as possible to avoid further damage. I recommend taking it to a trusted mechanic for a proper diagnosis.

I had a similar issue with my Audi A2 and it turned out to be a problem with the idle air control valve. Basically, it controls the amount of air that flows into the engine when it's idle. It's a relatively easy and inexpensive fix, so you should definitely have it checked out.

I would suggest checking the engine mounts. If they're worn or damaged, they can cause a rattling noise when the car is idle. It's best to have a mechanic inspect them and replace if necessary.