On hard acceleration my vehicle suffers from valve clatter, any ideas?
Valve clatter, also known as spark knock, ping and detonation, can be caused by a number of things. Basically the fuel/air mixture is igniting too soon in relation to the piston position. When this happens the resulting explosion is trying to force the piston down while the crankshaft and momentum or forcing it up. In time engine damage can occur. Octane in fuel helps to prevent the condition by slowing the burning process. On the engine, the knock sensor and EGR valve are two systems charged with preventing valve clatter. A malfunction of either system will make it much worse. Also a lean [not enough fuel in relation to air] fuel mixture will cause the condition. This can be the result of a vacuum leak or a faulty air flow meter, among other things. Ignition crossfire, caused by mis-routed spark plug wires is another cause. Finally excess carbon accumulation as well as other things can create the problem. For more information on valve clatter see our article Valve Clatter, Spark Knock
