Very short cold idles

[Rochev]

Of the 30+ vehicles I've owned the cold (high) idle lasts for a while. Of course the colder it is the longer it idles high. However on the newer Taurus's, the longest it's idled in 270k miles is about 15 seconds at about 0°F. Even at freezing temps (and obviously above) it idles at around 1300rpm for like 5 seconds and drops down. There must be a reason it's been designed this way, does anyone know why?

Cold idles generally slowly creep down to normal but these just drop right down after a short time like a sudden fuel cutoff. The old Taurus's will cold idle for an hour it seems.

 

[yaycandy]

Its real short on mine when real cold also. Most likely because of direct injection and the ecm has more control over the air and gas to keep it running smooth when cold. That and the old taurus' had an IAC that was controlled by coolant temp from the coolant flowing through it. I don't think the ecoboost has it, or I just haven't found it yet.

 

[krewat]

Fly-by-wire engines do not have an IAC, the computer is already controlling the throttle all by itself.

My three SHOs all did exactly this. They would idle down pretty quick. There is another small drop a few minutes later. When I (used to) leave work in the afternoon, it takes a minute to get to the main exit of campus. Waiting at that light, all my SHOs would idle down a little more at that light. Not sure if that was really an "idle down" for temperature, or sitting at a light that long, the PCM idles down a little more. Dunno.

It's really all about fuel economy and emissions.

 

[Rochev]

Good to know it's perfectly normal. My new Pathfinder idles high for a few minutes so that made me much more concerned. I know the transmission doesn't warm up idling but I'd feel better if the motor got going longer without being under load. I generally start moving after it idles down anyway