Shifting issues from 2-3 and 3-4 while driving with the manual high idle switch enabled

ransdell2

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Jan 25, 2017
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Anybody ever seen shifting issues from 2-3 and 3-4 while driving with the manual high idle switch enabled? Stopped at a red light at the bottom of a hill, started going up the hill and truck didn't want to shift to 3rd, got up to ~3500rpm, backed off the gas and got it to shift, then same thing going into 4th. Shifted fine thereafter (was cresting the hill at that point).

Pulled over, fluid levels checked good, not burned. Last change was about 13k miles ago. Manual high idle switch was on when parked (prior to these shifting issues) and forgot to turn it off when I started driving; I haven't done this before, so I have no history of anything weird while driving with the manual high idle switch enabled.

I turned off switch while pulled over. 108 degrees outside, trans temp about 175. Could not duplicate issues in auto or manually shifting with manual high idle switch off; have not tried with it back on. I was not on the throttle hard while climbing the hill, but it definitely should have shifted and normally does when starting from a stop at the bottom of the hill.

As far as I know the manual high idle being enabled (with the switch On) only causes the idle to elevate when certain conditions are met, such as:

The engine has been idling for more than 30 seconds.
The transmission is placed in Park or Neutral.
The vehicle speed is 0 MPH (0 km/h).
The ambient air temperature is less than 0 °C (32 °F).
The ECT is less than 68 °C (154 °F)
The brake, clutch and throttle pedals are not depressed.

Otherwise the computer treats it as if the switch were Off. Please correct me if I'm wrong on that.

208k miles on stock 2007 LBZ except for EGR blocker plate, manual high idle mod, and exhaust brake mod. No transmission issues other than this.
 

darkness

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All those are just for elevated idle when it’s cold. Manual high idle is pto related. I’m surprised it let you go to 3500. It should be limited to around 2200 rpm’s when on. Unless you changed the rpm in the tune. Don’t drive with the switch on.
 

Cougar281

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Sep 11, 2006
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Best bet is to take power for it through the switch from something that only has +12 when in park to prevent that from happening. If memory serves, I took power from something on the brake switch.
 
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ransdell2

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Jan 25, 2017
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I haven't done any tuning in the truck. I've posted in a couple of other forums and emailed John at Kennedy Diesel and the general consensus is just like you said, don't drive with the switch enabled. I always thought the first rpm level of high idle (~800-1000) was the same as elevated idle when it's cold enough, and the next two levels were more for PTO. Do you have any resources or links you can share that explain PTO or elevated idle? I understand the general idea of both, but am always open to learn more. Per a response on another forum, "[Manual high idle] will help with warming up engine although the factory high idle does better because it adjusts the turbo parameters and a few other parameters maybe."
 

ransdell2

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Jan 25, 2017
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Best bet is to take power for it through the switch from something that only has +12 when in park to prevent that from happening. If memory serves, I took power from something on the brake switch

Best bet is to take power for it through the switch from something that only has +12 when in park to prevent that from happening. If memory serves, I took power from something on the brake switch.
That's a great idea, I don't remember where I pulled power from. I'll check it out and post it in here.
 

ransdell2

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Jan 25, 2017
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That's a great idea, I don't remember where I pulled power from. I'll check it out and post it in here.
Looks like I added a 2A Add-A-Fuse to the 10A TBC ACCY, which is a keyed 12V source that powers the Body Control Module. I guess in the future I'll be finding something that only has 12V in Park to pull power from.
 

darkness

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I don’t have any links. But pretty simple though. Plenty to search, like which wire to tap into on the brake switch so you don’t need a separate switch to remember to turn off. But you should know pretty quick when you forget. I do it all the time on my Kodiak lol.