How do I fix a misfiring Audi 80 engine?

My Audi 80's engine has started to misfire and I'm not sure what the cause could be. The check engine light is on and the fuel consumption has increased. What could be causing this and how can I fix it?

First, you'll need to diagnose the issue by checking for any error codes and inspecting the spark plugs, ignition coils, and fuel injectors. It's also important to check the air filter and make sure it's not clogged.

Alternatively, it could be a problem with the fuel system. Check the fuel pressure and make sure there are no leaks in the fuel lines. It's also a good idea to clean the fuel injectors and replace the fuel filter.