2006 GT accelerates on its own then dies when driving slow

[Rei_h]

My 2006 Mustang GT convertible I bought used from a Toyota dealer last month is starting to do weird things. When I'm driving slow like in a parking lot, it revs up rapidly on it's own without me stepping on the gas pedal, then is dies. I put the gear in park (it's an automatic transmission) and it starts with no problem so far, but it's just really annoying. When it revs up, it's almost out of control. I step on the brake hard to try and stop it.

When it's running at a full speed, it has no problem whatsoever, and this problem is also very intermittent. It happened few times at night when I was at a store parking lots, but it did not happen at all the next morning when I was pulling out of my parking spot.

Could anyone please help me and give me ideas on what could be causing this? The Toyota dealership is 100 miles away, and alghouth I bought their warranty, I'm not sure if I want to take it back that far, it's also under 30 days from the purchase from the dealer, so if anything is wrong, they would have to fix it, wouldn't they??

Thanks for your help!

 

[VOORHEES]

100 miles or not, I'd take it back to them. Aren't the 05-09 "by wire" throttle also?

if so, definelty would get that looked at.

-J

 

[Rei_h]

100 miles or not, I'd take it back to them. Aren't the 05-09 "by wire" throttle also?

if so, definelty would get that looked at.

-J

What's "by wire" throttle mean? I am taking it to the local dealer tomorrow, and if they find the problem, I'll take it back to the dealer I got it from to get it fixed.... I drove it to lunch again today, and the problem didn't happen. It probably won't happen tomorrow at the service either, but I know this Ford dealership service is extremely nice, so they will be nice about it...

 

[SpartaPerformance]

"by wire" means there is no mechanical cable to actuate the throttle, it's done by an electrical signal to a motor on the side of the throttle body from control box on the end of the accelerator pedal. Is the vehicle completely stock? Is there a check engine light on?

 

[bradleyem]

"Throttle by wire" means that unlike older cars, there is no physical throttle cable between the gas pedal and the throttle body....it is all electronic and controlled by the computer. There is a stepper motor that opens the butterfly in the throttle body. The gas pedal has a potentiometer (variable resistor) to read the position of the pedal and send it to the PCM. I would look at 3 things:

First, get some carb cleaner and take the air intake tube off from the throttle body. Clean the inside of the throttle body with the carb cleaner. Also, be sure to open the butterfly with your finger and spray cleaner inside and get as much of the carbon build up as you can. Put the intake tube back on, making sure to reconnect all electrical connectors and hoses, and make sure that the clamps are all tight and everything seals well. The car will run a little rough at first until the carb cleaner burns off. Take it for a test drive and see if it acts up.

Second, there has been an issue with some of the early electronic throttle bodies. Have the dealership check/replace the throttle body.

Third, but less likely, is a problem with the electronic gas pedal assembly. Sometimes the potentiometer can get dirty or worn and cause intermittant problems as you describe.

Whatever you do, do not let the dealership blow you off. This is a safety issue, and if they can't fix it, then they need to find someone who can, even if they need to send the car to a Ford dealership.

 

[mjk]

I thought this was a joke at first... Bought the car from toyota and it accelerates on its own.. lol

anyways, I hope things work out for you. gl

 

[bradleyem]

I thought this was a joke at first... Bought the car from toyota and it accelerates on its own.. lol

anyways, I hope things work out for you. gl

That's a good one

 

[Rei_h]

LOL you guys are funny, didn't even realize the humor until I saw your post.
But in any event, I think this forum is awesome cuz your responses are probably right on the money. Here's what Ford service diagnosed me (it was expensive but now I can take it to the Toyota dealer service and tell them exactly what to do).

- PCM reprogram per tsb #8-18-2 1.0
- Engine decarb service (clean throttlebody as part of service)

Now, the car had a dead battery when I bought it, so I took it to Wal-Mart where the battery was from, and they replaced it with a new one. It was just over their 2-year warranty on the battery, so they only charged me a prorated amount, which I made the Toyota sales guy reimburse me. XD

I guess certain things needed to be cleaned/reset when the new battery was placed.

I'm not mechanically inclined, so unfortunately, I'd have to take it to a mechanic to do cleaning and all the things. This being within 30 days of purchase, I'm trying to get the Toyota dealer to do this at no cost to me under the implied warranty (it has limited warranty plus I bought extended warranty, which of course in this case won't apply). It does pose potential safety issues after all.

Thanks guys!

Wish me good luck...

 

[ski]

LOL you guys are funny, didn't even realize the humor until I saw your post.
But in any event, I think this forum is awesome cuz your responses are probably right on the money. Here's what Ford service diagnosed me (it was expensive but now I can take it to the Toyota dealer service and tell them exactly what to do).

- PCM reprogram per tsb #8-18-2 1.0
- Engine decarb service (clean throttlebody as part of service)

Now, the car had a dead battery when I bought it, so I took it to Wal-Mart where the battery was from, and they replaced it with a new one. It was just over their 2-year warranty on the battery, so they only charged me a prorated amount, which I made the Toyota sales guy reimburse me. XD

I guess certain things needed to be cleaned/reset when the new battery was placed.

I'm not mechanically inclined, so unfortunately, I'd have to take it to a mechanic to do cleaning and all the things. This being within 30 days of purchase, I'm trying to get the Toyota dealer to do this at no cost to me under the implied warranty (it has limited warranty plus I bought extended warranty, which of course in this case won't apply). It does pose potential safety issues after all.

Thanks guys!

Wish me good luck...

The idle speed normally becomes erratic whenever the battery is either disconnected or replaced. However, it should clear up after 20 miles or so of driving. If not, then there's a procedure in the battery maintenance section of the owner's manual that should facilitate smoothing out the idle.
But your problem is definitely more critical if you have to stomp hard on the brake pedal to stop the car without pressing the gas pedal, and resolving it as described in your post is the recommended way to fly.

Also, make sure your car has either the stock air intake, or an aftermarket air intake that's designed for a factory tune, if the PCM is going to be reprogrammed.
If it has an aftermarket air intake(CAI) that requires a custom tune(currently installed in the PCM), then the engine will not run correctly after the PCM is reprogrammed with a factory tune. If this is the case, and you do not have the handheld tuner that was used to install the custom tune, then you'll have to install either a stock intake or an aftermarket intake that's designed for the factory tune.

 

[Rei_h]

Well, after spending a day and a half at an independent mechanic who said the idle was low but didn't believe the reprogramming was needed, the Toyota dealer who tried to duplicate the issues, and another Ford dealer which the Toyota dealer took her to get them to duplicate the issues, my car decides she had anough attention. XD


The Toyota service did clean the throttle for customer satisfaction, but the other Ford service told them she had the latest software and repgoramming was not needed. They both drove her around trying to duplicate the issues but were not able to. Ford took care of some squeeky sound the brake pedal was having (I noticed that but didn't ask them to look at it..).

Other than that, no one basically did anything mechanical.

The car has been running great ever since. No more accelerating on its own or stalling. I have no idea what this was all about because I drove the car over 200 miles right after the battery was exchanged. It was still doing those things at that time. I would say after driving it over 500 miles and having different mechanics look at it, it stopped. Another mystery about this car...