Jones Junction discusses engine knocking in a recent post on its website.
Engine knocking means the air and fuel mixture in one of the engine's cylinders isn't the correct ratio, which makes fuel burn unevenly. A strong knock means the issue needs to be corrected as soon as possible or it could damage the engine, the posting.
Engine knocking could be caused by a fan clutch that slips, incorrect spark plugs, low coolant level, improper gas-octane level, carbon deposits on engine cylinder walls or problems with the cooling system, the posting said.
An octane-related problem can be resolved by reading the vehicle's manual to ensure the vehicle has the proper fuel type. Adding an octane booster can also correct the issue if the vehicle has the wrong octane fuel in the tank.
The vehicle also must have the proper spark plugs. The owner's manual will note which kind are correct for your vehicle, or a technician can check the vehicle for you.