Originally Posted by troverman

Define "cold." I've had two 2017 diesels and they absolutely and automatically idle higher at cold temps immediately after startup. We had 12F last week for a low, and in the morning the truck was idling around 1000 RPM instead of the usual 6-700. It gradually idles back down. Actual cold temps (below zero) would result in even higher idles.

There is a modification one can make using a resistor, an upfitter switch, and a specific wire in the blunt-cut bundles. I did this on my 2016 diesel. The value of the resistor determines the idle speed when the switch is flipped on. Some people use a rheostat instead of a resistor which allows for variable idle speed. In order for it to actually work, the truck must be in Park with the parking brake set. Once the brake is released, the truck idles down.

As for the purpose of high idle...the primary purpose is to power PTO-driven applications as someone above mentioned. Most people who wire in the mod here are using it for the purpose of preventing wet stacking, lessening the impact of extended idling on the DPF, having hotter heat, or better A/C.

Diesels don't warm up slower because they are burning less fuel. They warm up slower because they have much larger amounts of oil and coolant compared to an equivalent gas engine. The biggest problem a diesel has is that it uses compression ignition...meaning the heat generated by compressing the diesel fuel is what causes it to actually ignite. There is no "spark plug" electrically igniting the mixture. Only heat. That is why glow plugs are used to start an engine when cold. On a typical warm day, you'll barely see the glow plug light come on before it goes out on the dash gauges. But on a very cold morning, you might wait 2, 3, or more seconds before it extinguishes and then you can start the engine. Of course, many people with an ignition key starting system don't wait at all and the engine still starts. But if you have push-button start or if you remote-start the engine, the delay is forced by the computer.

Nevertheless, a certain temp needs to be reached for diesel to ignite under compression. Obviously, low idle speed will produce the least amount of heat while wide-open throttle would produce the most. So...we have an absolute temp that needs be be met in the cylinder for diesel to ignite...and we have an absolute value of heat produced by compression in a cylinder. What changes is the block temp. If the temp is -40F, the truck would have to compensate for a 100-gree difference compared to the same truck operating in 60F temps. The engine fan is also constantly cooling the engine block and coolant. I've operated in cold enough temps (-15F or so) where the engine temp gauge has shown fully warmed up during a highway run, but when stopping and idling for 10 minutes, the gauge would actually register a decreasing engine coolant temp. The 6.7L Powerstroke has a complex cooling system with four thermostats between the two independent cooling systems to try to maintain the best possible temp. The main cooling system, for example, can close the 201F thermostat and still keep the 194F thermostat open. This still allows engine cooling but at a lower volume to prevent over-cooling.

As the engine loses temp in bitter cold conditions while idling at normal low speed, what happens is the diesel does not combust as cleanly and fully. This creates soot (visible black particulate matter) which must be trapped by the DPF...filling it sooner and requiring sooner regenerations. It also eventually leaves a sheen of unburned diesel on the cylinder walls, which is the phenomenon known as wet stacking...which can be harmful to the engine.

Our 6.7L diesels have good computer management will can vary idle at any time and will idle up in cold temps and extended idling. But some choose to install the high idle switch which will, in fact, provide better heat and A/C performance, and less DPF usage.

Originally Posted by jimvan68

I installed the new switch I have a link for here https://www.dieselpowerproducts.com/...werstroke.aspx

I installed it in about 45 minutes. It worked great. I also had mine working in my 2010 F250 but had to hook up the up fitter switches to make it work. The 2017 can use this product and it is plug and play. Great product and easy to install with directions.

Originally Posted by AK_SuperDuty

Mine has high idle. I flip my #4 upfitter on, set parking brake, and it idles up to 1400 RPM's.

High idle helps warm it up faster, but more importantly it's much better for the longevity of the EGR system.

Originally Posted by jsavelli

I would like this. How to do I find out if mine has this or can I put mod through forscan on to allow upfitter 4 to put in high idle?

Originally Posted by jimvan68

The post before your questions has the link to the switch that is plug and play with 2017 Superduty. All you have to do is drill hole for dial and hide the wires.

Here is the link.

https://www.dieselpowerproducts.com/...werstroke.aspx

Originally Posted by jsavelli

I thought I read that this comes stock with some SD? through upfitter4 w/park brake on

Originally Posted by KubotaOrange76

cheaper option see post 93

https://www.ford-trucks.com/forums/1...-switch-7.html