Why does the Audi A4 engine make a ticking sound?

I have noticed a slight ticking sound coming from my Audi A4's engine while it is idling. Is this normal or could it be a sign of an underlying issue?

The ticking sound could be caused by several things, such as a bad spark plug or a loose valve cover, but it is most likely just the sound of the fuel injectors cycling on and off. If you want to be sure, you can take it to a mechanic for a quick check up.