I was driving 30 mph and stopped at a stop sign. Engine accellerates to 4,000 RPW with my foot on the brake. I shifted to neutral and the engine slowed to 800 RPM. What caused the car to accellerate while braking? 2000 Taurus with Duratec V6 auto. Thanks
car accellerates when braking ?
- Thread starter Jerryb
- Start date
- Status
Sounds like the car was not accelerating the engine was. On older cars I have seen the accelerator cable stick.
Make sure everything associated with the gas pedal and linkage is clean, rust free, properly lubricated, and not binding in any way.
Transmission downnshift when you hit the brake maybe? Or was it actually trying to accelerate?
Kestas
Staff member
I don't have an answer, but I wanted to mention my 01 Sable does something quite similar. Coming off the freeway, the car will not decelerate normally. Switching to neutral shows the engine revs at 1700 rpm. I also have the car lurch when I engage the transmission. I've cleaned the throttle body and replace the IAC motor, yet the problem remains.
4000 rpm is way up there, how accurate are you on that?
The Ford trans in that car is very well know for failure. The early symptom is while braking to a stop the down shift disingauges the trans instead of dropping to the lower gear.
Then on the restart a bang into 1st or needing to go back to neutral before it finds 1st.
I believe the over revv is a separate engine management issue possibly TPS or IAC. Do you ever spray down the gummy throttle plate?
Throttle cable can mess go bad.
The Ford trans in that car is very well know for failure. The early symptom is while braking to a stop the down shift disingauges the trans instead of dropping to the lower gear.
Then on the restart a bang into 1st or needing to go back to neutral before it finds 1st.
I believe the over revv is a separate engine management issue possibly TPS or IAC. Do you ever spray down the gummy throttle plate?
Throttle cable can mess go bad.
I know older emissions would actually bump the iac to make sure there was enough fuel mix to completely burn, rather than too high of a vacuum, resulting in incomplete burn and higher pollutants.
In my jeep, idle is 650 rpm. if I hit N while it's still rolling, it idles as 1100. Assume it's emissions, but could also be a safety margin to keep PS pump, etc., spun up.
If the engine was going WOT or even 1/2 throttle, you would not only fight that with brakes but also lose vacuum to the brake booster, making the pedal feel like concrete. how did the pedal feel?
M
In my jeep, idle is 650 rpm. if I hit N while it's still rolling, it idles as 1100. Assume it's emissions, but could also be a safety margin to keep PS pump, etc., spun up.
If the engine was going WOT or even 1/2 throttle, you would not only fight that with brakes but also lose vacuum to the brake booster, making the pedal feel like concrete. how did the pedal feel?
M
I've had this on a 2001 Ford Taurus before. What happens is that engine down shift and the brake pads are junk, not enough to compensate for the down shifted new torque and makes you feel that the car is launching forward.
The pad used? Not sure, my dad brought it to a mechanic that has Raybesto banner in the shop, most likely some service grade stuff.
Get better brake pads, this symptom went away when I put Hawk HPS on it.
The pad used? Not sure, my dad brought it to a mechanic that has Raybesto banner in the shop, most likely some service grade stuff.
Get better brake pads, this symptom went away when I put Hawk HPS on it.
I've had an issue where the engine wouldn't slow down with my foot off the gas--it would take a second or two to slow down--replacing the throttle position sensor cured it.
Originally Posted By: PandaBear
I've had this on a 2001 Ford Taurus before. What happens is that engine down shift and the brake pads are junk, not enough to compensate for the down shifted new torque and makes you feel that the car is launching forward.
The pad used? Not sure, my dad brought it to a mechanic that has Raybesto banner in the shop, most likely some service grade stuff.
Get better brake pads, this symptom went away when I put Hawk HPS on it.
brake pads may be to simple
I've had this on a 2001 Ford Taurus before. What happens is that engine down shift and the brake pads are junk, not enough to compensate for the down shifted new torque and makes you feel that the car is launching forward.
The pad used? Not sure, my dad brought it to a mechanic that has Raybesto banner in the shop, most likely some service grade stuff.
Get better brake pads, this symptom went away when I put Hawk HPS on it.
brake pads may be to simple
Most likely, dirty throttle body. The throttle plate is hanging up on some carbon buildup, sending wonky readings to the TPS, resulting in the surge.
It's really common, especially on that engine. I'd pull the throttle off and clean it and it's pretty likely that'll fix the issue.
Edit: if that doesn't fix it (it likely depends on how long it's been doing it), you may have to change the TPS. On that year, it's not integrated into the TB, so it should be pretty cheap to replace.
It's really common, especially on that engine. I'd pull the throttle off and clean it and it's pretty likely that'll fix the issue.
Edit: if that doesn't fix it (it likely depends on how long it's been doing it), you may have to change the TPS. On that year, it's not integrated into the TB, so it should be pretty cheap to replace.
Last edited:
Originally Posted By: JOD
Most likely, dirty throttle body. The throttle plate is hanging up on some carbon buildup, sending wonky readings to the TPS, resulting in the surge.
It's really common, especially on that engine. I'd pull the throttle off and clean it and it's pretty likely that'll fix the issue.
Edit: if that doesn't fix it (it likely depends on how long it's been doing it), you may have to change the TPS. On that year, it's not integrated into the TB, so it should be pretty cheap to replace.
This seems like the best answer. The car and engine was slowing down as I came to a stop. Then the ABS kicked in as the car and engine accellerated. The transmission does not slip when I drive. I did not press on the gas pedal and brake at the same time. When I shifted to neutral, the RPMs went down to 800 RPM while I still had my foot on the brake. Bad brake pads don't cause the engine to rev up.
Most likely, dirty throttle body. The throttle plate is hanging up on some carbon buildup, sending wonky readings to the TPS, resulting in the surge.
It's really common, especially on that engine. I'd pull the throttle off and clean it and it's pretty likely that'll fix the issue.
Edit: if that doesn't fix it (it likely depends on how long it's been doing it), you may have to change the TPS. On that year, it's not integrated into the TB, so it should be pretty cheap to replace.
This seems like the best answer. The car and engine was slowing down as I came to a stop. Then the ABS kicked in as the car and engine accellerated. The transmission does not slip when I drive. I did not press on the gas pedal and brake at the same time. When I shifted to neutral, the RPMs went down to 800 RPM while I still had my foot on the brake. Bad brake pads don't cause the engine to rev up.
I'm going to be different here and say you have an intermittent tear in your brake booster diaphragm. This caused a vacuum leak when it was flexed just right and subsequent high idle. Had something like this on a 91 dodge dakota 2.5/stick shift, never figured it out.
4000 RPM is gear and stopped? That is higher than the stall speed!
You have massive problems.
You have massive problems.
Originally Posted By: eljefino
I'm going to be different here and say you have an intermittent tear in your brake booster diaphragm. This caused a vacuum leak when it was flexed just right and subsequent high idle. Had something like this on a 91 dodge dakota 2.5/stick shift, never figured it out.
would not have even thought of this, but yes, could very well cause it. new inrush of air into the manifold, map sees it as throttle change and adds fuel.... voila.
I'm going to be different here and say you have an intermittent tear in your brake booster diaphragm. This caused a vacuum leak when it was flexed just right and subsequent high idle. Had something like this on a 91 dodge dakota 2.5/stick shift, never figured it out.
would not have even thought of this, but yes, could very well cause it. new inrush of air into the manifold, map sees it as throttle change and adds fuel.... voila.
But it was IN GEAR!
My car is 10 years old with and 75,000 miles and it never happened before. I cleaned the mass air flow sensor and the IAC. There was some carbon, but that's what I expected. Cables looked clean and moved easily with no crimps. Computers are strange and sometimes strange things happen. If it happens again, it goes to the shop, but I have little faith they can figure it out. Thanks for your help and advice.
- Status
Similar threads
