C3H6 would be an unlikely product, especially at combustion temperatures. The equilibrium products will be CO2, H2O and, if it is fuel rich as you suggest, CO, H2, and CH4. N2 will also be in the products (the major species) but will not appreciably react. Kinetic constraints could produce non-equilbrium products, but this will generally only happen at low temperatures and in any case will produce products such as soot, soot precursors, etc. Etylene is more likely than propene to form. However, at very fuel-rich conditions and at relatively low temperatures, C3H6 and a host of other unsaturated hydrocarbons may form.