This is the best definition I could find:
Spark knock (detonation) is an erratic form of combustion that occurs when multiple flame fronts occur simultaneously inside a combustion chamber. Detonation occurs because fuel is subjected to either too much pressure, too much heat or both. It usually happens during acceleration when the engine is heavily loaded and cylinder pressures are at their peak.
Instead of a single flame front growing outward smoothly like an expanding balloon from the point of ignition, multiple flame fronts are generated spontaneously throughout the combustion chamber as the fuel automatically ignites from heat and pressure. The multiple flame fronts collide, creating shock waves that produce a sharp metallic pinging or knocking noise.
Okay, that is what it is. Here are some things that can cause it.
cheap gas
overheating engine
ignition timing
lean fuel mixture
wrong spark plugs (too hot)
bad knock sensor
I hope this answers your question. Let me know if you have others.
Joe
Jul 6, 2010 at 7:53 PM
