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Run away acceleration on a Ford Windstar with 3.8 engine

After driving approximately 25 miles on the interstate and then getting off my 1999 windstar with the 3.8 engine began to accelerate by itself. I had to keep applying the brakes to slow it down. it never stopped accelerating the transmission would just slip allowing the van to slow. as soon as I removed my foot off the brake it began to pick up sped again with not indication of stopping. I was able to make it to my nieces home and park it and the trans was hot due to the slippage when I held the brake. Can anyone tell me what would cause the problem?? I never got a engine check light. I have changed the throttle position sensor just because I didn’t know what else to do. I was able to drive it back home after it had sat at my nieces house for around 3 to 4 hours with no problems. I changed the engine oil, oil filter, transmission fluid and filter because of the hearting problems when this occured. Thanks in advance for any help.

2 things connected to throttle lever. Cable from accel pedal and cruise control. Possible ur cruise servo went nuts.

I’m assuming by “slipping” you mean the automatic transmission torque-converter was slipping, not a manual and the clutch was slipping, right? Agree w/Cavell above, most likely either something like the driver’s side carpet was accidentally wedged up against the gas pedal, or some kind of linkage problem between pedal and throttle body and cruise control actuator (if you have cruise control). Might be a good idea to at least consult with a Ford dealership about this, maybe there is an already discovered problem affecting this make/model/year. And if it happens again, best to be prepared. Ask the dealerhip the option available: Does the car design allow the driver to safely turn the key to “off” with the engine running and transmission engaged to stop the engine in an emergency like this?

edit: One more thing, I recently cleaned the throttle body on my 20 year old Corolla, and while that one wasn’t that gunked-up, I could see a situation could develop when driving in a very dusty area or the like where the throttle body could get so full of gunk so as to cause the throttle plate to stick open. Might be worth it to have the throttle body checked, make sure the return spring is working and has the spec’d return force, and while at it, have the throttle body thoroughly cleaned.

The problem might be with the Idle Air Control valve. Ford’s have a history where the IAC valve can position itself where it allows the max amount of air into the engine.

When this happens, the O2 sensor see’s this extra air and the computer adds more fuel for this extra air and the engine rev’s.

A coworker with a Taurus with the 3.8L engine had this happen to them. Only in their case, when the engine rev’d, the vehicle took out two gas pumps.


Thanks tester I will check this. Would a IAC failure cause the engine check light to come on???

It could. It can cause a code P0505. Idle Control System Malfunction.

Some parts stores will pull codes from the computer for free. See if you can locate such a parts store.