That rhythmic knock under the hood could mean five very different things.

Your engine can make a lot of weird noises, depending on what has gone or is about to go fully kaput. If it's a rhythmic pinging sound that progressively increases as you step on the throttle, ...

Engine knocking can result from one of several issues involving your engine. Whatever is causing it, it must be dealt with immediately so it doesn't become any worse. The knocking is a warning sign ...