Why does my Audi 80's engine make a knocking noise while idling?

I recently purchased a used Audi 80 and have noticed a loud knocking noise when the engine is idling. It seems to go away when I accelerate, but becomes more pronounced when the car is in gear. What could be causing this and is it something I should be concerned about?

It sounds like you may have a problem with the engine's valve train. This could be caused by worn out or damaged components, such as lifters or pushrods. It's important to have this checked by a mechanic as soon as possible to prevent further damage to your engine.

The knocking noise could also be a sign of low oil pressure or lack of lubrication. Make sure to regularly check your oil levels and change it according to your owner's manual. If the problem persists, it's best to have a professional diagnose and repair the issue.

In some cases, a knocking noise while idling can also be caused by faulty spark plugs or ignition timing. Have a mechanic check these components and replace if necessary. It's important to address this issue as it can lead to poor engine performance and reduced fuel efficiency.