Why does my Audi A3 have a rough idle when starting?

I recently purchased a used Audi A3 and have noticed that it idles roughly when starting. What could be causing this issue and how can I fix it?

It is possible that your spark plugs may need to be replaced. Spark plugs are responsible for igniting the fuel-air mixture in the engine, and when they become worn or dirty, they can cause a rough idle. Try replacing your spark plugs and see if that helps improve your idle.

Another possibility is a dirty or clogged air filter. A dirty air filter can restrict airflow to the engine, causing it to run rough. It's important to regularly replace your air filter to keep your engine running smoothly.

A faulty oxygen sensor can also cause a rough idle in your Audi A3. The oxygen sensor measures the amount of oxygen in the exhaust and sends this information to the engine control module. If it is faulty, it can cause the engine to run rich or lean, resulting in a rough idle. Consider having your oxygen sensor checked and replaced if necessary.