Why is my Audi A6 engine making a strange clicking noise?

I recently noticed a strange clicking noise coming from my Audi A6's engine. It seems to happen when the car is idling or at low speeds. What could be causing this and how can I fix it?

The most likely cause of the clicking noise is worn valve lifters. It's a common issue for Audi A6s and can be easily fixed by replacing the lifters.

Another possible cause could be a faulty timing chain tensioner. This can also cause a clicking noise and should be checked and replaced if necessary.