How to identify the noise of Peugeot 30 1 engine?

Distinguish whether the sound source comes from outside or inside the engine. The engine cover is loose, the bottom fastening is loose, and there is not enough oil? Or is the noise increased due to poor combustion? If the combustion is not good, try to clean the throttle and injector, and then use some fuel additive products to improve the combustion, that is to say, the combustion in the combustion chamber should be synchronized to remove carbon deposits and reduce noise.