Why is my Audi engine making a strange knocking noise?

I recently purchased a used Audi from a private seller and have noticed a strange knocking noise coming from the engine. It seems to occur mostly when the car is idling or accelerating. What could be causing this and is it something I should be concerned about?

It is possible that the knocking noise is due to an issue with the engine's timing belt. If the belt is worn or damaged, it can cause engine components to knock against each other, resulting in a loud noise. It is important to have this checked by a mechanic as soon as possible to avoid further damage.

Another potential cause of the knocking noise could be a problem with the fuel injectors. If they are clogged or not functioning properly, it can cause a knocking sound in the engine. It is recommended to have them cleaned or replaced to resolve the issue.