https://pic.armedcats.net/a/an/anonymous/2008/07/26/coldiac.jpg
https://pic.armedcats.net/a/an/anonymous/2008/07/26/coldloop_000.jpg
O.K basically, yes it is to overcome greater internal friction when the engine is cold and the lower amount of vaporization of fuel when the motor is cold....Oh btw this is only on a normal port fuel injected spark petrol engine. Diesels etc, no idea, however I belive they are the same.
These graphs are a pain in the arse for tuners two create, because if you put too much fuel in you'll foul the plugs or too little and it won't run toooooo crash hot. One reason I refuse to become a tuner...lol :lol: The little tweak at the end of the IAC map is to assist in hot starting...
These two graphs where dumped off my race car engines computer, you'll notice when the motor is cold, the IAC (Idle Air Control) motor is "more open" and the air fuel ratio is around 12:1 which is on the rich side
Technically these two graphs are then compared to the base idle map (on GM based EFI systems) before being actually used, but it shows what is basically going on. The computer these maps come from is a GM Delco 808 EFI computer from the Mid 80's. Wonderful little things. Not all GM's stuff is crap, EFI computers is one are where they really kick arse...well at least compared to other Japanese or Alfa Romeo computers I have to deal with :lol:
As far as emissions go when the poor 'lil motor is cold: They are S**t. Since we are dumping in bulk fuel to get the motor to function the AFR is wrong so the CAT won't function and the unburnt hydrocarbons and CO are terrible.
EDit:
Also the CAT converter converts unburnt hydrocarbons into CO2 and water, which would explain the presence of (some) water in your exhaust.