How do vehicles produce carbon monoxide & Nitrogen oxide???

Production of carbon monoxide by vehicles :
Carbon monoxide is formed by incomplete combustion of the fuel (i.e. petroleum gas, petrol or diesel) of vehicles.

Production of nitrogen oxide :
In the internal combustion engines of vehicles, nitrogen and oxygen in air react together in the presence of sparks to give nitrogen monoxide gas.
N2(g) + O2(g) → 2NO(g)