As the title states, the engine knocks and it doesn't always stay knocking. Usually it starts up fine and starts knocking within a few minutes, Then it will go away for a while, and then come back. It just comes and goes and doesn't make any sense to me. When the problem first developed if you turned the car off and then back on, the noise went away.. which made me think it was a sensor or computer issue. However now it does not go away when you restart it. I have attached a video because I am at a loss and I'm just hoping it doesn't need a rebuild of any kind.