I'm not sure about knocking because it was not knocking when I had it a few days ago but did you change the battery out? The battery that was in it will not hold a charge which is why I had to keep cables on it for it to idle properly and not have the car die out on me.... and yes it did KIND OF sound like the video when the cables were not connected.. only there was not any knocking. It was just a bad idle from not having any power until the car shuts off due to lack of power.