Vvehicle surges forward when applying brakes?

[Stormin-Norman]

I have a 2003 Windstar SE that sometimes when I apply the brake the vehicle wants to accelerate, it did it twice yesterday, once in a parking lot & the other time driving slow through town. I did some research this morning on the internet & found several people complaining that the brake pedal & the gas pedal were to close together and that it may be possible to accidentally press the gas pedal while applying the brake. I don't think this is what is happening but it may be. I just wondered if anyone had any input on this. I wear a size 12 Xtra wide shoe and have never had this on any other vehicle.

It is possible that there is a problem with the brake booster causing an increase in RPM when applying the brake?

[12Ounce]

Originally Posted by Stormin-Norman

.....It is possible that there is a problem with the brake booster causing an increase in RPM when applying the brake?....

Yes, a leaky booster can cause the symptoms you describe. As the throttle plate is closed, limiting intake air ... a sudden rush of air from a leaky booster can cause a brief rev-up.

[wiswind]

I was NOT able to locate the power brake booster check valve in the aftermarket for my '96.
You may have to go to the dealer for it.
It was included with the power brake booster units.....but you do not want to replace the whole thing for this little, easy to replace part.

Another possible cause is a sticking Idle Air Control (IAC) valve.
When you move your foot over to press the brake, the computer takes over the idle speed by opening the IAC to keep the engine from stalling.
Stalling is the MOST common failure under this condition as the IAC sticks and does not open fast enough.
However, it is possible for it to stick in the other direction.....causing a idle speed "overshoot".
This is not a common thing, but is possible.
Cleaning the IAC would be something that I would put on the list.

The problem can be made worse by the fact that the transmission is downshifting.
A sticking Torque Converter solenoid can cause this.
Solenoid being a fluid valve that the computer activates....electrical signal to open/close it causing fluid flow that engages or disengages the torque converter.
In this case, you get a boost of power because the transmission is engaging when you don't want it to.
This "should" cause the O/D light to flash or the Check Engine Light (CEL) to light (and stay lit) when it happens.....storing a code that tells you that this is what happened.

[Windstartled]

Originally Posted by wiswind

Solenoid being a fluid valve that the computer activates....electrical signal to open/close it causing fluid flow that engages or disengages the torque converter.
In this case, you get a boost of power because the transmission is engaging when you don't want it to.
This "should" cause the O/D light to flash or the Check Engine Light (CEL) to light (and stay lit) when it happens.....storing a code that tells you that this is what happened.

This happens to me in combination with the rough idle I always experience when the engine is cold. But the O/D light is only flashing when it's wintertime otherwise it doesn't but the van still "hiccups" and wants to leap forward when stopped in Drive with brakes applied. This does not happen once the engine is warm though. Actually the rough idling only begins once idle speed transitions from high to low, but stops once engine has reached normal operating temp. I've been meaning to troubleshoot this but the van being 12 years old it has other, more pressing issues that require my attention. It is quite annoying still.