Raymond J. Henry wrote:
> Err... Are you aware that the PCV valve (when properly functioning)
> prevents backfiring from igniting crankcase fumes?

A friend of mine failed emissions and "fixed" it by pulling out the PCV
valve and hose to lean the mixture, and he plugged the PCV hole with a
spark plug. His car passed, but when he later removed the valve covers
to fix a leaky gasket, the valve train and inside of the cover were
coated with very soft tar.