Car question

[BigV]

Originally Posted by ZenGum

I love it when you can fix a machine by thumping it. Very primal. RAWR! Og mad! Og Smash! [thwack ... vroom!!] Bwahahaha!

the technical term is "percussive maintenance". It is very satisfying no matter how effective it is.

Originally Posted by ZenGum

Oh, and as well as the above ... you are using the recommended grade of gas, aren't you?

gas grade is a measure of the octane in the fuel. Octane's role is to change the point at which the fuel / air mixture spontaneously combusts due to the heat from compression. You experience this as "knocking". It is most common when the engine is under a heavy load such as hard acceleration or towing or driving hard uphill. The mixture detonates before the piston reaches top dead center and/or the spark ignites an already lit combustion chamber and the result is a hard knocking sound. I've never heard of octane having much if anything to do with idle loads.