Tell if the knocking is heard at idle but goes away at higher RPMs. Is it only when the engine is cold or when it's warm? Tell about the car's age and what engine. Knocking or tapping sounds are common. Often these are valve related or can be an injector. If this happens at idle, you might want to get an automobile mechanic's stethoscope to help locate the area of the noise.
Does anyone know what the knocking sound can be in the car? I took it for inspection but they couldn’t figure it out

Chowhound
Comic Vine
GameFAQs
GameSpot
Giant Bomb
TechRepublic