Why do internal combustion engines only burn to carbon monoxide, not dioxide?

Why don't diesel and regular car engines burn all the way to $\ce{CO2}$?




I think this is sort of covered by [What really happens atomically in an explosion?](https://chemistry.stackexchange.com/questions/15995/what-really-happens-atomically-in-an-explosion) because the burning of the fuel air mixture is basically an explosion. The point is that there isn't a nice simple answer because the reaction is fearsomely complex.


Actually most of the fuel does burn to carbon dioxide. The proportion of carbon monoxide is quite small. In a normally tuned engine there is enough oxygen to burn all the fuel to carbon dioxide but the fuel/air mixture isn't in the cylinder long enough for the reaction to go to completion. You probably know that all modern cars are fitted with [catalytic convertors](http://en.wikipedia.org/wiki/Catalytic_converter), and what they do is to complete the reaction as the exhaust gases pass through them.


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