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2015 F150 Lariat Screw 3.5
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Discussion Starter #1
So I have a 2015 F150 screw with the 3.5. 6" lift on 37s with under body armor and rock sliders welded to the frame.

I routinely take my truck through trails and into environments that FoMoCo probably never intended this truck to go to and be put through.

Here is the really weird issue that maybe one of you have experienced or know of.

I will be in either 4H or 4L, and chewing my way over an obstacle, whether that's a group of rocks, a rock ledge, or in todays case extremely deep sand on an incline. I was in M2 with the locker engaged, and was steadily chewing through the sand and climbing up a very soft section of a hill climb out at the dunes here in Vegas, and out of the blue the truck just stops cold turkey. No wrench light, no pop up info box saying check this or that, no chime, no CeL, nada. I could press the accelerator to the floor and the motor will not come off idle. I literally have to switch back to N, rotate selector switch to 2H, shift to P, then back to N and back to 4H or 4L to get throttle response back. This has happened to me several times before in the past and its always the same solution, and "almost" always the same scenario that causes this issue. High wheel speed, low vehicle speed (I:E; clawing up a rock ledge, scrabbling up a gravely hill climb, chewing through soft sand) seems to make my truck go into some sort of protect mode. I am tuned by MPT on the 91 PR-X so Idk if this is a torque management issue or not, but shortly after my truck did this, my friends 2020 2.7 powered screw F150 attempted the same hill and despite him running 35s and being stuck in my ruts I made, he was under full throttle significantly longer than me and now once did his truck ever go into a protect mode. Our other buddy has a 18 screw 5.0 F150 and his truck was cutting power on him, but nothing like my scenario, and he is not tuned at all.

I have no ideas other than perhaps torque management? Nothing I can think of to google this issue comes up with any viable situations and solutions that others may have found or experienced. I've even called dealerships and talked to techs, parts guys, shop leads, master techs, and not one of them have any idea wtf is going on. I've never experienced anything like this in my 14 Fx4. I was stuck in a mud hole in that thing and had the throttle pegged to the limiter with the 5.0 in it, and never once did it go into any sort of "protect" mode.

Strangest thing, again, is the absence of any pop up warning box, or code, or any chime of any sort that would alert you to an issue.

Is my possessed?
 

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2013 Ford F150 XLT 3.5 Ecobeast SuperCrew 4X4
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Are the other 2 trucks also tuned by MPT ?
 

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I agree that it's odd that you didn't receive any kind of dashboard alerts. It's obvious that the pcm is intervening and it is doing so because it is responding to measured parameters that are triggering the intervention. Those same triggers are normally tied to alerts.

I too wonder if the tuning has inadvertently nipped the alerts? (or if that is even possible)

You could test that next time by returning to stock and repeating the scenario?

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Since he’s ankle deep in sand I’d also wonder about wheel speed sensors acting up.
 

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Discussion Starter #5
Thanks for the responses guys.

First off, no. My truck is running MPT, the 2020 is 5Star, and the 18 is stock.

I could probably run out and return to stock and see what changes. By that measure I could also try stock and my 5star tunes as well.

Wheel speed sensors seems odd. I've had them go out from deep water crossings before, like a 35 inch tire deep, but there's distinctive pop-ups that happen and symptoms. Cruise control will absolutely not work, it gives me a pop up saying 4x4 disabled, service advancetrac, stuff like that.

I emailed MPT and they have requested datalog files. Which means taking my laptop clear across the city of las vegas to the dunes and getting it to trigger again. That's the weird bit. This doesn't always happen. Not sure why they would need data logs to tell if they adjusted my torque management or convinced the pcm to relax on some parameters.

Last night it triggered on one particular hill climb, but didn't on about 6 others. The only note-worthy scenario difference is the last hill climb requires you to slow down significantly 3/4 up to take a sharp right around a grouping of rocks and when doing so you have to climb up and over, or through in my case, a large berm of sand which meant very slow vehicle speed, but high wheel speed. This scenario would make you think WSS, but the whole no CeL, no pop up, no nothing makes me wonder whats up, and again, this didn't happen to the other 2 trucks.
 

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As you described, wheel sensors sending unexpected data WILL engage various decisions by the pcm, but they SHOULD be accompanied by dash alerts.

Really strange that the truck is making decisions, apparently, but not complaining to you via alerts

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Discussion Starter #7
So my truck is possessed by my wife?
 

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Discussion Starter #8
But on a serious note, that does seem very odd that the PCM would do things and there not be a clear reason why, or a dialogue box that would give me an idea of what's happened.
 

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Any stored codes?

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Discussion Starter #10
You know, I don't know honestly. When I head out later to drop some stuff off, I'll check with my x4 and see if there's anything.
 

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Have you tried doing the same run, but in stock mode? This would eliminate whether the problem is something Ford did to the 3.5 Ecoboost. Or is it related to your tune from MPT.
 

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Discussion Starter #12
No I haven't. I probably wont be able to get back out there for a while but I'll be sure to try multiple tunes.
 

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What RPM are you turning when this happened? Could low speed knock be causing the problem? KM
 

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Discussion Starter #14
Being in low range and usually 1 or 2? At the point it happens it is mostly 3k or higher. No performance degradation up to when it happens either, its literally "all is well....all is well....nothing".
 

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Discussion Starter #15
Here's an idea of what I do with the truck.

 
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2013 Ford F150 XLT 3.5 Ecobeast SuperCrew 4X4
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Apparently I am missing something. 🤷‍♂️
 

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I have no idea what sensors are used to do this, but my Super Duty "knows" if it thinks the right pedal is stuck (under the floor mat or electronically) and drops all power. Because of your description, I wonder if the F150s have something like that also.
 
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I have no idea what sensors are used to do this, but my Super Duty "knows" if it thinks the right pedal is stuck (under the floor mat or electronically) and drops all power. Because of your description, I wonder if the F150s have something like that also.
Hmmmmm. That's interesting.
It kinda does sound like once it is "triggered", the throttle position sensor is just ignored. (until a key cycle)

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Could this be related to the angle of incline of the truck when operating it under those conditions? I am thinking if a fluid pickup starts sucking air maybe there is a trigger in the ECM. Does it do it on flat ground? Decline?

Another thought is maybe there is some fail safe in there for the transfer case or transmission when you're chewing on stuff for an extended period of time?
 

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Discussion Starter #20
I don't know. I've never really been on flat ground and digging through sand or such to have it trigger. I run 37.13.5's and aired down to 15psi I practically float over the sand when going over level/levelish ground.

I've driven up 31* inclines and driven back down them with no issues at all other than just being steep.

I wouldn't imagine it being a fluid pickup ordeal, as both of my friends took the same hill and had no issues like mine.
 
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