Why does my Kia Rio's engine make a knocking noise?

I recently noticed that my Kia Rio's engine has been making a knocking noise while idling. It's never done this before and I'm concerned that there may be something wrong. What could be causing this and how can I fix it?

It’s possible that there is an issue with your engine's fuel injection system. If the fuel injectors are dirty or clogged, it can cause a knocking noise. You may need to have them cleaned or replaced by a mechanic.

Another potential cause could be low quality or old fuel. It's important to use high quality gasoline in your Kia Rio. If you've recently filled up with a low grade gasoline, it may be causing the knocking noise. Try filling up with a higher grade and see if the noise goes away.

Sometimes, this knocking noise can be caused by a build up of carbon deposits on the cylinders. This can be prevented by using a fuel additive specifically designed to clean the engine. You can also have a mechanic perform a decarbonization service.