ping and bad MPG

[geezerstiva]

but it runs perfectly. if i blew a hole in a piston it'd be missing. bad. i may be messing with it this weekend, and i had a thought--could it be the oxygen sensor? i believe its the original one, and my other car did this, just a whole lot worse. changed the o2 sensor and it ran great.

[SIBladerunner]

it sounded like u had a detonation problem, run a compression test to b sure

[phantorn]

The lean mixture and running hotter, pre-ignition, does not come from hot spots but rather from heat of compression. .

So then detonation is the coliding of 2 flame fronts like spark and a hot spot?[/quote]

[geezerstiva]

no, no dieseling (thats what i call it). it just pings going down the highway. and weird thing is, if i put the gas pedal down further, it stops!

[jglutz]

Phantom....the heat of compression (adiabatic...scientifically) is just normal physics. Whn ever something is compressed, it gets hotter, the atoms are closer together and the atoms collide with each other causing heat. During the normal 4 cycle process...the fuel expands...which adds cooling....the compressed air always gets hot....without enough fuel...not enough cooling is added....thus at ignition...hot compressed air and less cool fuel results in hotter combustion. this might not make sense but it is hard to explain without going into whats called the Carnot Cycle.

Or think of it this way...

When the cylinder ignites....the mixture turns into heat energy....when the heat energy can not be absorbed by the head or cylinder walls...the ignited mixture coverts the heat energy into expansion energy which pushes the cylinder down. Not enough fuel (lean)...all of the heat energy is absorbed and little is left for expansion....thus to go faster...more RPM's are required to produce more expasion...thus more heat absorbed...and so on...and so on....

Hot spots in pistons only happen after a very long period of running lean.