Engine knock is the sharp, metallic sound that cuts through the hum of a healthy engine. At its core, engine knock is a problem of timing. In a knocking engine, parts of the air-fuel mixture don't ...

A young person approaches a home, rings the doorbell (maybe knocks too) and runs. It's a centuries-old prank that at its best is a harmless annoyance for victims. You may know it by its playful names: ...