Idle

Stigg

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Fort Worth, TX
I don’t know if any of you have noticed this or not. I’m in Fort Worth and it has been very hot lately. This morning it was 80ish and the idle on my truck is right around 500rpm like it always has been. However, when it gets 100-109 I have noticed, and even took my truck into the dealership, to see why my truck would high idle to 750 to 1,000rpm.

Have any of you experienced or noticed this?
 
I don’t know if any of you have noticed this or not. I’m in Fort Worth and it has been very hot lately. This morning it was 80ish and the idle on my truck is right around 500rpm like it always has been. However, when it gets 100-109 I have noticed, and even took my truck into the dealership, to see why my truck would high idle to 750 to 1,000rpm.

Have any of you experienced or noticed this?
Interested to see what some others that are closer to the engineering and maintenance on these trucks say…maybe @wutang61 ? My logical guess would be it’s probably under additional load keeping systems cool - AC, tranny, engine coolant, etc - and therefore high idles?
 
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Yeah, me too. It sure is weird. But I have noticed the difference on lower and high temperature. I don't know what else could do it.

The most irritating thing is that when it idle's high like that it also affects the braking. I notice that I have to apply them harder.
 
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Interested to see what some others that are closer to the engineering and maintenance on these trucks say…maybe @wutang61 ? My logical guess would be it’s probably under additional load keeping systems cool - AC, tranny, engine coolant, etc - and therefore high idles?
There no way to absolutely nail it down without live data, but many things can call for increased RPM.

Electrical demand and ECT are probably the recipe.

The faster the engine spins the more the water pump…pumps. Idle is a no load condition and the heat output increase is negligible compared to coolant flow.

Also, the fans on modern vehicles are VS (variable speed) long gone are the clutch fan days or high and low. Combine that with the AC calling for full cool and the interior blower motor on high you have significant amp draw on top of the regular loads. Alternators make more power at increased RPM.


The braking thing though puzzles me. The T1 platform are the first trucks without vacuum assist brakes. These trucks are hydroboost now to save the space from the diaphragm pancake. If you do notice any difference, it’s because everything is just plain hot in 100+ ambient.
 
I don’t know if any of you have noticed this or not. I’m in Fort Worth and it has been very hot lately. This morning it was 80ish and the idle on my truck is right around 500rpm like it always has been. However, when it gets 100-109 I have noticed, and even took my truck into the dealership, to see why my truck would high idle to 750 to 1,000rpm.

Have any of you experienced or noticed this?
I'm in Naples Florida and the average daytime temp now is about 96 to 98 degs with a real feel of 112 degs and my truck idles around 750 rpm. At night it stays around 600 with a temp of 85 degs.
 
I get what Huntredi is saying and that makes the most sense. As far as the braking, I had a 2017 Chevrolet diesel High Country that high idled a lot. Both of these trucks braking acted the same way when they idled faster. It’s like the higher rpm’s and momentum just make the brakes feel sloppy. Just so you don’t think I’m a good, I’ve included some pics from today at a full stop at lights.

The first one is this morning around 8:00-8:30p at 89 degrees. The second was at 2:00p at 104 degrees.
 

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Here's mine at 730 pm at 109°F at about 750ish. Here's one at 68°F st 300 pm at about 650ish.
 

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