What is the cause of the engine knocking sound in my Audi A4?

I recently noticed a strange knocking sound coming from my Audi A4's engine. It seems to be happening only when the car is idling. I'm wondering what could be causing this and if it's something I should be concerned about.

The most common cause of an engine knocking sound is low oil levels or dirty oil. Make sure to regularly check your oil levels and change your oil according to your car's recommended schedule. Also, consider using a high-quality synthetic oil for better engine performance.

Another possible cause could be a faulty spark plug or fuel injector. These should be inspected and replaced if needed to prevent any further damage to your engine. It's always a good idea to have your car regularly serviced by a trusted mechanic to catch any potential issues early.