When driving a petrol-engined car, pinking
is a symptom of maladjusted ignition timing, or using
an incorrect grade of fuel.
The ignition timing is responsible for causing a
spark at the correct moment so that the petrol-air
mixture ignites as the piston is on its power stroke.
For maximum power, the explosion should occur when the
piston is as close to the top as possible without actually
being at the top. This means that the mixture is fully
compressed, and the explosion will exert maximum force on the piston.
Pinking occurs when the explosion happens as
the piston is exactly at the top of the stroke; the
crank, connecting rod and piston are all in line.
In this position, the explosion attempts to push the piston and conrod through the crankshaft via the
big end - not a good situation.
When an engine pinks, there will be a sudden
loss of power and an accompanying noise - a high-pitched pinging rattle rather like a diesel engine on start up.
Allowing pinking to continue can cause serious damage
to the engine very quickly, although the problem is alleviated temporarily by adjusting your driving style.
The immediate solution to alleviate the problem is to
drive more conservatively, completely avoiding hard
throttle at low revs. This should get you to a service
station or to your home if you are going to attempt your own repairs.
Assuming you are using the correct grade of fuel, the long-term solution is to retard the ignition timing slightly so that the spark occurs further around the cycle
and the explosion occurs after the piston has passed top dead center. Retarding the timing too far will not cause problems up to a point, but power and efficiency will be lost to some degree.