Unintended Acceration

vxr500

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Had a weird instance where revs just kept climbing under heavy throttle in 3rd. Took out of gear right away, pulled over and shut down. Was bouncing off rev limiter for about 5 seconds though.

I do have one of those sprint boosters that wires into your pedal and shortens the drive by wire delay and increases the throttle per input based on a numeric value you can enter. I’ve used it for 7 months and never had an issue. But I shut it off anyway.

It started up fine a few minutes later and didn’t repeat. It ran fine all the way home. I took the intake off to see if there was an obstruction near the throttle blades, but none. Just a little dirty so I cleaned it.

I’m hesitant to turn on the sprint booster again, but that sucks because I really liked the improved throttle response.

Anybody else have a similar issue? Could it be something else?
 

msvela448

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You are the first person I've heard that is using a device to change the throttle ramp rate. I'd venture to say that is most definitely your problem. Take that thing off and see if the problem happens again.

By the way... Why not just use a handheld tuner? Ask the tuner you use to change the throttle ramp rate in the tune so you get the response you are looking for... No trickery by a third party device... It's just written into the tune using Ford's computer so all the safeguards are in place for a drive by wire system.

For example... In the tune... you can tell the computer that when the pedal is pressed 10%, open the throttle blade 20%. Of course the problem with this is that the car feels like it falls flat on the top end, or when you "floor it" because the back end of that throttle ramp rate curve is flatter to make up for the extra opening on the front end. In other words.. As an example... After 50% throttle it takes 2-3% pedal to open the blades only 1%. So even though the car initially felt strong because very little pedal movement equated into big throttle blade movement... You have to make up for it somewhere and consequently, later in the curve, more pedal movement actually equals less throttle blade movement.

This was on old "trick" tuners could use to make consumers believe that the tune was making more power, when what was really happening is the computer was just opening the throttle blades more, with very little pedal input, thus the driver feels "whoa... This thing has power now".

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vxr500

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One of my first mods was an SCT 91 tune. I was hoping it would help with the throttle response, but it really didn’t. Is there a screen on there that allows me to fine tune that, or do I need to download a custom tune?

I hear you on the sprint booster. It does feel a little flat at anything over half throttle on the full race setting. But another thing it does besides multiply the throttle value, is shorten the signal time. It really did seem to wake up the soft bottom end of the 4.6.

I contacted them about the issue, and they claimed it’s almost impossible for that to happen. But of course they’re going to stand behind their product. Who knows? Maybe my rubber mat got hung up?

I’m going to try it on again in an open area and see if I can duplicate the issue. But if I can get a tune to do what it does, I might be interested in going that route.
 

MrAwesome987

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I contacted them about the issue, and they claimed it’s almost impossible for that to happen. But of course they’re going to stand behind their product. Who knows? Maybe my rubber mat got hung up?
When I first got my car, the PO had some thick rubber mats in it. I revved it when I got it home showing off, and the throttle got stuck on the rubber mat. It bounced off the limiter a time or two before I could get turn it off. I immediately removed the rubber mats and did without until I got some of the OE Ford carpet mats.
 

07 Boss

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You are the first person I've heard that is using a device to change the throttle ramp rate. I'd venture to say that is most definitely your problem. Take that thing off and see if the problem happens again.

By the way... Why not just use a handheld tuner? Ask the tuner you use to change the throttle ramp rate in the tune so you get the response you are looking for... No trickery by a third party device... It's just written into the tune using Ford's computer so all the safeguards are in place for a drive by wire system.

For example... In the tune... you can tell the computer that when the pedal is pressed 10%, open the throttle blade 20%. Of course the problem with this is that the car feels like it falls flat on the top end, or when you "floor it" because the back end of that throttle ramp rate curve is flatter to make up for the extra opening on the front end. In other words.. As an example... After 50% throttle it takes 2-3% pedal to open the blades only 1%. So even though the car initially felt strong because very little pedal movement equated into big throttle blade movement... You have to make up for it somewhere and consequently, later in the curve, more pedal movement actually equals less throttle blade movement.

This was on old "trick" tuners could use to make consumers believe that the tune was making more power, when what was really happening is the computer was just opening the throttle blades more, with very little pedal input, thus the driver feels "whoa... This thing has power now".

Sent from my SM-N975U using Tapatalk


Yep, all that thing does is up the voltage signal from your pedal to make the computer think you pressed the pedal farther than you did. It accomplishes the same thing as just pushing the pedal in farther. It does not do a single thing for performance or mileage as ads claim. It just pushes the pedal down farther than you think so it seems like there is a difference but in reality there is none. It's a gimmick.
 

vxr500

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Yep, all that thing does is up the voltage signal from your pedal to make the computer think you pressed the pedal farther than you did. It accomplishes the same thing as just pushing the pedal in farther. It does not do a single thing for performance or mileage as ads claim. It just pushes the pedal down farther than you think so it seems like there is a difference but in reality there is none. It's a gimmick.

I realize what it is, and did not think it made more power. But it does give better throttle response, which seems to be programmed real slow on the 4.6.
 

vxr500

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When I first got my car, the PO had some thick rubber mats in it. I revved it when I got it home showing off, and the throttle got stuck on the rubber mat. It bounced off the limiter a time or two before I could get turn it off. I immediately removed the rubber mats and did without until I got some of the OE Ford carpet mats.

I’m thinking it’s a possibility. I have those thick Ford all weather mats and it was not anchored
 

msvela448

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There is no screen on the SCT that you can change to throttle rate. It has to be done by a tuner with a custom tune file.

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07 Boss

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One of my first mods was an SCT 91 tune. I was hoping it would help with the throttle response, but it really didn’t. Is there a screen on there that allows me to fine tune that, or do I need to download a custom tune?

I hear you on the sprint booster. It does feel a little flat at anything over half throttle on the full race setting. But another thing it does besides multiply the throttle value, is shorten the signal time. It really did seem to wake up the soft bottom end of the 4.6.

I contacted them about the issue, and they claimed it’s almost impossible for that to happen. But of course they’re going to stand behind their product. Who knows? Maybe my rubber mat got hung up?

I’m going to try it on again in an open area and see if I can duplicate the issue. But if I can get a tune to do what it does, I might be interested in going that route.


Yeah, whomever is doing your tuning just have them ramp up throttle response. You can't shorten the signal time. Electricity moves at a certain speed. If anything it is getting slowed down because it has more wire and electronics to travel through before it gets to the ECU. With that said your pedal is just a potentiometer and there may be some actual physical lag from when the pedal first moves before the brushes hit the metal strips. You can either bend the little brushes or you can add something to the pedal between the the pedal arm and the housing, basically like pre-pushing the pedal a hair to take up that physical slack. You don't have to worry about the computer thinking your stepping on the gas if you do it too far because the pedal should recalibrate. There is a manual procedure to set the calibration but I think it does it periodically. Here is what I did with just some vhb tape which was later replaced by some layers of lead tape. It is probably about 1/16' thick built up on the pedal arm.

 

RED09GT

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The canned SCT 91 tune doesn't have much of a change from stock for throttle response.
You need to buy a tune from one of the vendors that sells tuning. As stated above, they can manipulate the amount of throttle opening proportinal to the amount of pedal movement.

I personally would not use a throttle booster on anything other than the stock tune. Use one or the other, not worth risking losing control over the throttle of your car.
 

golkhl

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There is a way to re-calibrate the gas pedal, with the key on and the engine off, slowly push the gas pedal to the floor and release.
 

vxr500

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Planning on a custom tune this fall since I added the BBK x pipe. I'll see if I can get it adjusted then.

I know a lot of you guys are down on this throttle changer thing, but it really did change the character of the car at lighter throttle. Was way more fun to drive around town and snappier off the line. I just need to find a more reliable way if it's defective.


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vxr500

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Yeah, whomever is doing your tuning just have them ramp up throttle response. You can't shorten the signal time. Electricity moves at a certain speed. If anything it is getting slowed down because it has more wire and electronics to travel through before it gets to the ECU. With that said your pedal is just a potentiometer and there may be some actual physical lag from when the pedal first moves before the brushes hit the metal strips. You can either bend the little brushes or you can add something to the pedal between the the pedal arm and the housing, basically like pre-pushing the pedal a hair to take up that physical slack. You don't have to worry about the computer thinking your stepping on the gas if you do it too far because the pedal should recalibrate. There is a manual procedure to set the calibration but I think it does it periodically. Here is what I did with just some vhb tape which was later replaced by some layers of lead tape. It is probably about 1/16' thick built up on the pedal arm.


That looks interesting. Can you give a little more detail on that. Is it going under that space in the lever?


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dark steed

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Yeah the factory throttle response is a bit sluggish. But even my first Bama tune (pre-AM days) really woke it up and got rid of the slow rpm decay.
Then I got a Lito tune...[emoji41]


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MrAwesome987

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Yeah the factory throttle response is a bit sluggish. But even my first Bama tune (pre-AM days) really woke it up and got rid of the slow rpm decay.
Then I got a Lito tune...
emoji41.png
The slow throttle decay is probably worse than the terrible throttle response. I don't see how anyone could withstand that.
 

07 Boss

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That looks interesting. Can you give a little more detail on that. Is it going under that space in the lever?


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Basically when you step on the gas it moves a brush or set of brushes over some strips of metal. Depending on where the brushes are on the metal strips determines the voltage. Being mechanical and with manufacturing tolerances, you may have some pedal movement where nothing happens. Either the brushes have not contacted or traveled far enough along to produce a signal. If you can move your pedal a little bit without a change in rpms, this is what is happening. My car had almost a 1/4" of travel before the motor would recognize any movement. Maybe not that much but it seemed like a lot. Anyways, at rest the pedal arm rests against the housing there. I just put a brick on the pedal and applied some foam tape to the arm so it would not go all the way back up when at rest. Careful with the brick while your head is down there. That pedal will snap back up with a vengeance and can hurt. Don't ask me how I know this, just trust me. After I felt that it actually worked I used a permanent spacer of a few layers of lead tape replacing the foam tape. Basically what this does it puts the pedal to a point where there is an actual readable signal and then with the re-calibration it sets that point as idle. Now as soon as the pedal moves there is an immediate change in signal where as before there may have been some pedal movement before an output signal was even produced. This just removes the actual mechanical dead space and nothing to do with ramping up the signal or anything. Here is the pedal at rest. It may not look like a big change but at the end of the pedal that little bit is quite a bit of actual pedal movement.

 

vxr500

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Basically when you step on the gas it moves a brush or set of brushes over some strips of metal. Depending on where the brushes are on the metal strips determines the voltage. Being mechanical and with manufacturing tolerances, you may have some pedal movement where nothing happens. Either the brushes have not contacted or traveled far enough along to produce a signal. If you can move your pedal a little bit without a change in rpms, this is what is happening. My car had almost a 1/4" of travel before the motor would recognize any movement. Maybe not that much but it seemed like a lot. Anyways, at rest the pedal arm rests against the housing there. I just put a brick on the pedal and applied some foam tape to the arm so it would not go all the way back up when at rest. Careful with the brick while your head is down there. That pedal will snap back up with a vengeance and can hurt. Don't ask me how I know this, just trust me. After I felt that it actually worked I used a permanent spacer of a few layers of lead tape replacing the foam tape. Basically what this does it puts the pedal to a point where there is an actual readable signal and then with the re-calibration it sets that point as idle. Now as soon as the pedal moves there is an immediate change in signal where as before there may have been some pedal movement before an output signal was even produced. This just removes the actual mechanical dead space and nothing to do with ramping up the signal or anything. Here is the pedal at rest. It may not look like a big change but at the end of the pedal that little bit is quite a bit of actual pedal movement.


Got it. So you’re just starting the pedal movement at a further point. Thanks!
 

07 Boss

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Got it. So you’re just starting the pedal movement at a further point. Thanks!
Exactly. It just takes up any dead space your pedal may have. Some cars are worst than others and some don;t need it at all.
 

DieHarder

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Actually, I've experienced the same thing (unintended/delayed acceleration after letting off of the throttle). Happened to me several times. Once, when I was doing a tuning run. Took my foot off of the throttle but the rpm's just kept rising (and I'm supercharged so things happen real fast). I'll admit I wasn't entirely sure what to do for a second but hitting the brakes brought the rpm's down and drove it home without issue. Only seems to happen under full throttle and most often when the engine is just hitting it's maximum torque. A bit concerning to say the least. It's been doing it since I've owned the car. Asked my dealer/tuner about it after the run but it's like telling someone you saw a UFO; everyone always thinks it's carpet/interference related or something else. I can tell you it isn't. It doesn't happen all of the time but when it does it's hold on for dear life until you get it under control again. If I had to hazard a guess I'd have to say there's some throttle/programming interdependency taking place where the computer is trying to satisfy a given throttle input that the engine is still working to complete that is overriding the throttle release command. At least I'm glad to hear there are other cases of phantom acceleration besides mine.
 

Bigdaddybry

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Are you saying that the RPMs kept climbing even after you let off the throttle? If so, then yes, it’s some kind of throttle issue. If you’re saying you were trying to accelerate and it went to the limiter, it may be that the clutch is slipping. So the question is, we’re you on of off the throttle when it actually happened? Did it feel like it was in neutral? Or was it haulin ass?
 

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