Ambient temperature has another effect, it changes the density of the air.
Density is weight/unit volume warmer air is less dense colder air is denser.
Warmer air weighs less and therefore has less weight of Oxygen, and burns less fuel, and visa versa.
Todays ECU's take into account inlet temperature, and in warm conditions will inject less fuel decreasing power output, and again the opposite with colder air = more Oxygen = more fuel = more power.
These adjustments are also monitored by the O2 sensor in the exhaust system, with O2 high it would be asking the ECU for more fuel, and O2 low it asks for less fuel.
There are similar effect due to changes in height or barometric pressure.
These effects should be less noticeable in an engine with a turbo.
Carburettors had difficulty with this problem.
It is interesting to note, a turbo compressing the air raises it's temperature, loosing some of the gain from the turbo.
Some cars have an Intercooler fitted to cool the air between turbo and engine to overcome this effect.
Cold start is a different problem, it is more to do with a cold inlet manifold catching and holding petrol droplets, so the mixture arriving in the cylinder is too weak to fire.
Once the manifold gets warm any droplets hitting the wall will quickly evaporate, and re-join the flow into the cylinder.
Engines that inject fuel into the manifold can take advantage of the cooling effect of evaporating petrol.
With carburettors this cooling could cause the whole thing to freeze up even in summer, until manufacturers learned to heat the inlet by casting the exhaust and inlet manifolds in one piece or water heat the inlet, and/or the carburettor.
