[DistanceGuy1]

Here are some thoughts for you:

Using gas with a low octane rating can cause knocking. Always use the octane rating recommended by the vehicle manufacturer. With gas prices increasing, many owners have switched to a lower octane fuel in order to save money.

In addition, anything that increases combustion chamber temperature can cause knocking such as failure of the EGR, a cooling system problem, burning engine oil, or incorrect spark plug heat range.

A too lean condition, such as a PCM, fuel system or a vacuum leak problem, can also cause knocking.

On an older vehicle, especially one used primarily for stop-and-go driving, deposits can build up in the combustion chamber leading to the hot spots that cause knocking.