Why does my Audi A2's engine produce a knocking sound at low speeds?

I recently bought a used Audi A2 and noticed a knocking sound coming from the engine when I'm driving at low speeds. It doesn't happen all the time and seems to be worse when the engine is cold. What could be causing this and how can I fix it?

The knocking sound you're hearing could be caused by the engine's timing being off. This can happen over time due to wear and tear on the timing belt or faulty components. It's important to get this checked and fixed by a professional mechanic as it can lead to further damage if left untreated.

Another possible cause of the knocking sound could be a dirty or clogged fuel injector. When the fuel injector is not clean, it can lead to an uneven spray of fuel into the engine, resulting in a knocking sound. Have your fuel injectors cleaned or replaced to see if it solves the issue.