Dead throttle at high elevation
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4wd Low
Joined: Jun 2008
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Dead throttle at high elevation
My '12 6.7 is giving me a dead throttle while starting from a stop at high elevation...but ONLY in gear, starting from a stop and ONLY at high elevation (above 8500'). Once moving, no problem. 2 footed, 1 footed, power brake, no difference. (as in, it won't power brake, won't rev or at all while in gear.) In park or neutral it will rev.
My 2002 7.3 did not do this. I was routinely at high elevation (several times a month). I just bought this truck last spring, and have only been stopped above 8000' on two occasions and it did it both times. Once was in Silverton, CO, every time I started out from a stop. The other time was last weekend, getting to an aid station at 9800'. On the switchbacks, I had to put it in 4low so that it would even move at idle. Same issue maneuvering while at the site, and then returning the next morning.
Turning off traction control didn't help. Neither did whatever gets turned off when you hold down the traction control button for a while. 4hi didn't help, the tires weren't in any danger of spinning.
No issue at all while moving, same power as usual (which doesn't seem to be as much as expected) but no hesitation or anything. No hesitation at normal elevation of 4300'.
My 2002 7.3 did not do this. I was routinely at high elevation (several times a month). I just bought this truck last spring, and have only been stopped above 8000' on two occasions and it did it both times. Once was in Silverton, CO, every time I started out from a stop. The other time was last weekend, getting to an aid station at 9800'. On the switchbacks, I had to put it in 4low so that it would even move at idle. Same issue maneuvering while at the site, and then returning the next morning.
Turning off traction control didn't help. Neither did whatever gets turned off when you hold down the traction control button for a while. 4hi didn't help, the tires weren't in any danger of spinning.
No issue at all while moving, same power as usual (which doesn't seem to be as much as expected) but no hesitation or anything. No hesitation at normal elevation of 4300'.
Posting Guru
Joined: Feb 2018
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I would say you are encountering a brake-over-throttle fault. I'm not saying you are on the brake, but that the truck thinks you are. And I have no idea why it would do this only at high elevation unless it is just a coincidence and maybe it's related more to the angle of the truck. Maybe the stop light switch is in need of adjustment. Just a WAG. My plan B is your truck is possessed but I don't have a strong theory for that.
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4wd Low
Joined: Jun 2008
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I would say you are encountering a brake-over-throttle fault. I'm not saying you are on the brake, but that the truck thinks you are. And I have no idea why it would do this only at high elevation unless it is just a coincidence and maybe it's related more to the angle of the truck. Maybe the stop light switch is in need of adjustment. Just a WAG. My plan B is your truck is possessed but I don't have a strong theory for that.
A faulty brake switch was the cause in other threads I read, but I was thinking the elevation element would rule that out. Maybe not?
Mountain Pass
Joined: Sep 2005
Posts: 189
Likes: 37
From: Ethel WA.
You might have an air bubble in one of the rear brake lines, when you go up in altitude the bubble expands and locks up a wheel. Jack up each side and see if there is a drag on the brake. If so then all you need to do is flush out and bleed your brakes. If it return after bleeding the brakes you have a leak or crack in a fitting or line. Tracing that type of leak can be real fun.
Good luck
Smokeploe
Good luck
Smokeploe
Thread Starter
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4wd Low
Joined: Jun 2008
Posts: 13
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You might have an air bubble in one of the rear brake lines, when you go up in altitude the bubble expands and locks up a wheel. Jack up each side and see if there is a drag on the brake. If so then all you need to do is flush out and bleed your brakes. If it return after bleeding the brakes you have a leak or crack in a fitting or line. Tracing that type of leak can be real fun.
Good luck
Smokeploe
Good luck
Smokeploe
Mountain Pass
Joined: Dec 2009
Posts: 224
Likes: 7
From: Regina, Saskatchewan
Maybe you could use or borrow a scan tool and look at the throttle demand settings while this is happening and see if there’s an issue there?? Make sure the truck is pointing downhill😜😩
Posting Guru
Joined: Feb 2018
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That might help. With throttle by wire, if there is a disagreement between the pedal and the throttle on the engine, the engine will go to idle and it will pitch a code. With brake-over-throttle, the engine goes to idle, but won't pitch a code.
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4wd Low
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New development, the last couple times I've started it and driven it, for the first couple seconds it has a dead throttle. This is at normal elevation of 4200. Today it was actually a little bit worse and lasted as long as it took me to idle forward from where it was parked in the street and then back into my driveway, as I was backing up it started to be responsive.
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Joined: Oct 2015
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From: Wyoming
I recently had my F-350 above 9,000' elevation with zero issues. Check the brake fluid level. Open the cap and see if any pressure is released. I doubt that's going to help, but it won't hurt. Otherwise, maybe an issue with the mass air flow sensor?
Thread Starter
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4wd Low
Joined: Jun 2008
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New development, the last couple times I've started it and driven it, for the first couple seconds it has a dead throttle. This is at normal elevation of 4200. Today it was actually a little bit worse and lasted as long as it took me to idle forward from where it was parked in the street and then back into my driveway, as I was backing up it started to be responsive.
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