Originally Posted by Massey

Engine knock has a specific harmonic that the sensors are calibrated to detect. The sensor can detect a knock well before we can hear it. Actually if we can hear the knock then it is strong enough to cause damage to the engine. Try running better fuel, fuel additives (safe for Cats). If you are burning any oil that will lower your ignition point of the fuel and cause knocking no matter what grade of fuel you use. It dont take much oil do cause this.

Massey