High Idle due to cold weather

[aruth55]

Recently here in Chicago we’ve been seeing very cold temperatures. Today it was around 10 degrees on my dash. My car warms up as normal, but then my idle stays at around 1000rpm when it normally drops to 800rpm after reaching operating temp. If I drive the car and come to a stop it settles straight to 800rpm and requests an 800rpm idle. After a bit of idling though, it again raises to 1000rpm and requests a 1000rpm idle, but this is after oil cools down a bit from my Mishimoto oil cooler, so I believe the car is raising the idle slightly to keep oil within operating temperature ranges because it is so cold out, because if it stays at 800rpm the temperature of the oil continues to drop well below operating temp to 160-155 degrees F and continues to drop. Any opinions? Car has sat for about a week otherwise so nothing would have magically started leaking, also checked over everything just incase and nothing seems to be leaking as well. Thank you!


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[Business6]

My oil temps drop precipitously in the winter once I come to a stop. I've had it go into the upper 150s/low 160s on occasion as well.

But for the idle staying high my thoughts are either a slightly stuck throttle plate or, to coincide with the oil temp drops, it's just trying to keep it at a more efficient operating temp.

 

[blakewillingham]

I have noticed that mine will do this when the temps are around 20°F and below once warmed up. Probably to keep the engine warm. Shouldn't be anything to worry about.

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[Intuit]

Prior car had an overcooling issue to the point could barely get any heat out of the core. It eventually got bad enough that it would go in/out of open loop mode; marked by very sudden high idle only seen with cold starts. This was an EEC-IV (pre OBD) system.

Newer engine control designs in general, seek to control temperatures *MUCH* more tightly than older ones.




For the motorcycle with an older design, I can see as much as an 18MPG swing just based on ambient temps. Just covering the radiator gets much of that back. The newest generation of my same bike, runs the engine wwaayy hotter. (emissions)

 

[Sam4]

I think I read in here that it settles itself down. I would say that if its continuing to hunt for rpm's to 'heat up' it maybe a weak thermostat?
I almost went with - 'snowboots resting on the pedal and cramped up mats...' but I resolved to be less dad-like in 2022. Threw out my khakis.

 

[xxiaze]

It's a normal function of the vehicle to get it to operating temp more quickly. All of our fiestas do this. I also experience this and live in Wisconsin with very similar climate to you. Do not be alarmed. If you watch your coolant temp in accessport it will fall from higher RPM at a specific temp every time.... I forget exactly what the number is but it's 100 or something around there. Try it out a few times and it's systematic nature will comfort you. If for whatever reason your car does NOT do this like clock work there may indeed be something else going on but I'm willing to bet it's a non issue as it's been discussed and I've experienced myself many times.

 

[M-Sport fan]

It is right at 122*F coolant temp that this happens on mine, every time, at least according to the Ultra Guage.

 

[Intuit]

............. If I drive the car and come to a stop it settles straight to 800rpm and requests an 800rpm idle. After a bit of idling though, it again raises to 1000rpm and requests a 1000rpm idle, ...........

Don't know what the ECU is requesting but did observe this exact same behavior this evening. It was 11°F this morning and 19°F this evening.

Because it hadn't been started since Sunday and was curious how the battery was holding up, held the accelerator to the floor before and during the crank to prevent start. Battery read 9.3v during cranking. (11.9v IIRC before) It's not that old but failed to check charge level before throwing in the car. So I don't know whether it was maintained above minimum storage level while on the store shelf. The AGM are supposedly sensitive about charging so I try not to over-concern myself with voltage levels. Extended cranking was slow but stable. https://www.fiestastforum.com/threads/agm-battery-concerns.24120/

 

[aruth55]

Based off what everybody has said I’m attributing it to an “overcooling issue” with my Mishimoto oil cooler and radiator combined with temps well below 10degreesF. Will update whether it continues or not when things warm up!


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[Intuit]

I failed to mention that my drivetrain and programming are stock, and observed what you saw, following a 25~30 minute drive parked in the driveway.

 

[M-Sport fan]

What I noticed tonight, albeit not as cold as everyone else on here is currently seeing (~24*F), is that when I had my defroster on to clear the melted on snow/ice on the windscreen, the car took FOREVER to even reach 150*F coolant temps (and it never got hotter than this if I kept the defroster, and therefore the AC compressor, on, whether idling or driving) because of the high speed fan keeping the coolant from heating up (is my guess ).

Once I switched to the regular heating vents with no defroster, the temps climbed steadily to the normal 185*F to 190*F range.

 

[aruth55]

Well the verdict for me ended up being my car overcooling because of my cooling mods combined with such a low temperature, as soon as the temperature went above about 20 degrees F car went back to idling at 800rpm, not needing to stay at 1000rpm to be able to stay at operating temps.


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