I am having an issue with my 2005 Mustang. A couple of months ago the car would not slow down after I took my foot off of the gas. After I stopped and took my foot off of the brake the RPM's went up to 1500 and the car accelerated to about 30 mph without me touching the pedal. I parked it and revved the engine to about 4000 RPM's and the RPM's kept going up and down from 3500 to 4000, while I was holding steady on the gas pedal. After that the car stalled and went into Fail Safe mode. After I turned off the car and restarted it and it was fine. Took the car to the dealer and they replaced the A/R sensor and the ERG valve. A couple of days ago I had the same problem and I took it back to the dealer and they found no problem with it. I got the car back yesterday and today the acceleration problem happened again. When I turned off the car and restarted it the problem went away. I am also having a problem with the RPM's dropping when the car is stopped and and in gear with the A/C on. The RPM's usually drop a little but it is noticeable, sometimes the drop is significant enough to shake the car and almost stall it out. Has anyone else had this problem or heard of this? Any information anyone could provide would be appreciated.
Thanks

 

Once I had the car accelerate on me as you are describing. I was stopped at a redlight and my rpms started rising. Freaked me out enough to just turn off the igniotion as it was about to break loose. Popped the hood, scratched my head and then started her up again never to get this again. That was about 4 months ago. My idle was fine though. Also no error messages were thrown. I dunno what could have caused it, at the time my car had about 6,000 miles on her.

 

Sounds like it is a bad throttle body. The throttle is electronically controlled, so there is no mechanical cable or anything going from the gas pedal to the engine. Your foot sends a signal to the cars computer, which then sends a signal to the throttle body motor to open up the throttle. If the TB motor is bad, it could freak out and do whatever it wants and you would have no control over it.

Also, side note, the V8 model cars have no EGR, so you must have a V6? That would help in the future if you tell us what engine you have, and any mods you may have.

 

It could also be the throttle position sensor sending bad signals to the computer.

 

That is true, either way you need to take it to the dealer and have them diagnose the problem. It could be potentially dangerous if it decides to take off on it's own at the wrong time.

 

Maybe your car is a Decepticon.

 

I've wondered about that too... It felt like a wild horse just wanting to sprint.

 

Thanks for the input guys. It is a V6 with everything stock. The servicer metioned the throttlebody when I brought it in, but then couldn't duplicate the problem. It definately sounds like something in the electrical system or the "brain" of the car. Anyway I'm taking it back in on Monday and they will keep it for a few days to see if they can find and fix it.
Thanks again

 

Mine does the same thing. Sometimes revs up to 2,100 rpm. Often when the revs are dropped as in starting in heavy traffic (V6 5 Speed). Took it to the dealer more than once.

They won't do anything until they can "capture data" on their black box.


Let me know if you find anything, and I'll do the same.


Mike

 

It's most likely the TB positioning sensor, either from the pedal to the computer, or from the computer to the TB. Ive also had problems like that in other cars, with the carburator at stoplights. Our 84 CJ7, if it hasnt been run in a while, you have to keep some gas on it at stoplights, and slowing down, or it will shake and conk out; and that sucks because then the power steering and brakes become immensely hard to operate.

 

I had a VW bus do this to me once.... turns out the throttle is actually held closed by a spring, and the spring broke causing it to go wide open....good thing the terminal velocity of a VW bus is still only about 45 mph (whether it is on the road or dropped from a C130). A VW bus can't scare anyone...EVER.

 

Got the car back today. They never did see the problem, but they replaced the accelerator pedal and the throttle body and motor assy, along with the throttle body air intake. So far it seems good although I only drove it a little. I sat idiling in gear for a few minutes and the RPM's did not drop once. So hopefully this does it.
Thanks,
Brian

 

It worked out good for you that they changed all with new parts to solve your problem quickly. It doesn't say much for their diagnostic skills though. Ford must love it when they receive a pile of parts for warranty claims when only one part is probably defective.

 

Mine has done this after a hard acceleration. it wouldn't back off. scared me to death. it has done this twice so far.

 

2 Or 3 Times... In One Year!

 

name your car "carrie"

 

that sounds like your oxygen sensors...
or maybe a bad fuel filter.

 

LMFAO!!

Seriously, try to clean your throttle body (take it off the car and clean) first.

 

This is what happens with you delete the throttle cable and replace it with drive by wire.

 

It also happened to me...GT500 I accelarated hard and it did not come down after I let off the accelarator...It did it 3 times!! it turned out that it was the floor mat...somehow it got bunched up behind the accelarator and was not allowing the gas pedal to go back to the normal position. I check the floor mat everytime I get into my car just to make sure that the floor mat is in the right position. Has not happened again...