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Transmission/Shifting Stall !!!!!!!

Messages
32
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Location
Parkton, MD, USA
#1
I have recently brought my ST in for what I perceive to be a fairly significant transmission/shifting issue.

The issue happens often when I’m attempting to pass someone. Keep in mind, we all have a high performance and very fast vehicle. :)

If you accelerate as if you’re about to pass, let off the gas suddenly (in my case where I can’t quite pass yet), and then hit the gas hard...the vehicles loses all its powers/hesitates/and almost feels like The engine is stalling.

I can reproduce this every time now but the dealership is telling me nothing is wrong. This almost got me killed the first few times when I had no idea what was going on and I’ve never experienced this in the car before. Now I have to be somewhat gentle when I accelerate or pass a car in my $60k sport tuned vehicle??? WTF?

Has anyone experienced this? Can anyone also simulate or reproduce this?

I’m sorry Ford but this is a big issue and it needs to be addressed.


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Messages
32
Reactions
20
Location
Parkton, MD, USA
#3
Yes, it doesn’t matter what drive mode I am in. Are you saying this doesn’t happen to you at all and that you can’t force this to happen?


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Messages
230
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95
Location
Cincinnati, OH
#4
Yes, it doesn’t matter what drive mode I am in. Are you saying this doesn’t happen to you at all and that you can’t force this to happen?


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I've never experienced any power loss after taking my foot off the gas and step on the accelerator again to the point where it feels like stalling. That's really scary. I wonder if you can reach out to Ford and have a regional manager look at it or take it to another dealer.
 
Messages
32
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20
Location
Parkton, MD, USA
#5
I recall the technician telling me something about the throttle body and how it needs time to open and close if you suddenly gas it, let go of the gas momentarily, and then gas it again. Still, this should never happen what I’m experiencing.


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STFan

Administrator
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106
#6
I bet the stalling and loss of power your experiencing is the excess fuel in the chamber that wasn’t burned because there wasn’t enough air getting through when you let off the gas. Either way it’s still very scary in real world driving.
 
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114
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44
Location
North Hampton, NH, USA
#7
Try another dealer. Better yet, try another st from your current dealer.
Not sure why you would stab it without assurance of a clear lane but.....
 
Messages
32
Reactions
20
Location
Parkton, MD, USA
#8
Not even stabbing it....just accelerating...doesn’t matter how much gas you give it. Shocked nobody had this issue given my dealer said this is “normal”. I will try another dealer. Thanks!


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Messages
2
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0
Location
Jersey Shore, PA, USA
#11
Any update on this? I'm going to go give this a try. We have a '21 ST with 5700. My wife complained of something similar, only difference, our ST will tell her to pull over and restart the engine. She also stated the auto start light on the dash flashes when it happens. She can't recreate it on demand and hasn't yet figured out what she is doing when it happens. It's never happened to me and I drive it more then her. Last happened while merging on to the highway. We took it to the dealer and they also couldn't reproduce and it isn't logging an error.
 
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Location
Knoxville, TN
#12
There are a lot of things going on mechanically that take time when you do this depending on speed and demand:

1. ECU "sees" demand via accelerator pedal
2. "demand" transmitted to CAN bus
3. ECU uses appropriate map to open throttle body and alter cam position to max torque. Throttle body with variable camshaft tuning is NOT linear, thus the reason you see the DBW throttles with variable cams.
4. TCM sees "demand" from CAN bus, and (depending on condition) unlocks torque converter and downshifts appropriately and may adjust duty cycle on AWD clutches
5. Vehicle accelerates.

Now a lot of stuff is going on and it takes time. Now you let off, possibly dramatically, and most of this happens in reverse order. However you're now going faster and you repeat acceleration event so possible explanations :
The ECU/TCU may simply be slow to respond to another event in succession
The ECU/TCU may be programmed to limit response to immediate, dramatic changes in demand for any number of reasons
Torque converter unlock, lock, unlock may be slow and may not happen at all.

SInce you're moving faster, the demand may not be seen as extreme as before so response is delayed
There are so many possibilities in this scenario, that I would likely guess it's probably both limited in response time, and in being able to readjust all the above mechanical parts in such quick succession. There could also be ECU/TCU strategies to limit torque output in such a scenario.

You might try doing this in Manual mode to see if you have the same issues. But, to be honest, this isn't a big torquey V8 mounted to a manual transmission and a direct wired throttle. Unless it throws a code the average tech is going to tell you it's normal.
 
Messages
32
Reactions
20
Location
Parkton, MD, USA
#13
I have noticed that this problem cannot be recreated in sport mode. But it does happen in every other mode. It just means that I have to be more conscious about my driving style and be much more gingerly if I’m not in sport mode.


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Messages
162
Reactions
89
Location
Knoxville, TN
#14
It would make sense that Sport mode doesn't do this, as the some of those steps are not being taken, for example letting off in Sport applies engine braking- meaning the engine didn't immediately unlock the torque converter and upshift some number of gears. Therefore you don't get all the same hesitation when you floor it again. I thought I read above it did happen in Sport mode.
 


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