What does it mean when a rod starts knocking in the motor?

When a rod starts knocking in a motor, it typically indicates a problem with the engine's internal components, particularly the connecting rod or bearings. This knocking sound is often caused by excessive clearance between the rod and the crankshaft, leading to metal-to-metal contact and potential damage. It can signify insufficient lubrication, wear and tear, or even a failing engine. Ignoring this symptom can lead to catastrophic engine failure, necessitating immediate attention.