I had a thought about this issue while reading my new New Car
Features manual. The Prius has a catalytic converter to reduce
emmissions, but that only works when it is hot. (This has been
mentioned; that is one reason the ICE runs when cold, to get the
converter working). The other part is that there is some other sort
of chemical bed which the exhaust goes through that adsorbs
hydrocarbons when cold. This adsorber collects the HC while
everything is cold, and then when it is heated up, the hot exhaust
running through it gradually removes the adsorbed HCs and runs them
through the (now hot) catalytic converter.
I'm wondering if the ICE may run when it is warm in order to be sure
that the adsorber is purged so that just in case the next start is
cold, there will be some adsorbtion capability left. I can't use
this to explain all the cases of ICE-always-starts, but I don't
understand how the computer keeps track of the HC load the adsorber
has, and under what circumstance what happens. I do know there is a
valve in the CC which determines whether the adsorber is in purge
mode or not.
--- In toyota-prius@y..., "Georgia Pritchett" <georgia@c...> wrote:
> > In my 6 months and 6000 miles, the gas engine has started every
> > single time that I turn the key to "start" -- even when the
> > warmed-up and the AC is off.
> That really surprises me. Up until October, we could get a no ICE
> start anytime the car had been off less than 2 hours and anytime it
> was parked in the sun during the day. So I could get one if I ran
> out at lunch or even some evening (depending on where I was in our
> lot). Salinas runs a tad cooler than San Diego during the rainy
> season (it ain't winter by any stretch of my imagination :-).
> We were unusually sunny during August and September (October is
> our warmest month). Do you park in the sun?