Sudden Acceleration on 200

[dudeigota66]

I have a daily driver 200 in my mustang that has recently decided to accelerate itself. I drive it for a little while and all of a sudden the pedal gets pushed in all the way and the car goes into full throttle. I shift into neutral and the acceleration stops; minutes later it does it again. what can cause this? The only major change is the drop in elevation of the car. I set it at about 3800 ft and now im living at around 1000ft. This is very strange cause the pedal is pulled in with strength and when i shift into neutral i feel a heavy thump and the car stops. Any help would be great thanks guys.

 

[bubba22349]

One thing to check is the condition of the motor and trans mounts old worn out ones sag and can cause linkages to bind

 

[69.5Mav]

Sounds like broken motor mounts.

Open the hood.

Set the parking brake.

Step fully on the brake.

With some one standing on the side only, never in front-Danger-.

Put the car in gear and lightly rev the engine.

If the engine moves more then1/2" then the motor mounts are broke.

As the engine twists it pulls the throttle linkage closed this futher pulls the throttle closed.

You need to get this fixed imedeatly as the engine twisting like this has been know to jam the transmission linkage so that you can't get it out of gear. This is a problemthat is not very common any more but used to be more frequent when your car was new.



Bubba, your response went in as I was typing mine but I agree with you.

 

[dudeigota66]

The transmission has been vibrating lately, would replacing the tranny mount fix this and the acceleration?

 

[69.5Mav]

The transmission has been vibrating lately, would replacing the tranny mount fix this

Most likely, Yes.

and the acceleration?

I do not believe so. The engine has to twist up and with just a trans mount broken you would not get enough movement. I blieve you have at least one motor mount broken possibly both. Time to change all the mounts.

 

[oldgrezmonke]

I also first thought of a broken motor mount - the "thump" pretty much says it . The motor mounts in older cars did not have designs that restricted the movement if broken so I suggest a repair be made as soon as possible . The motor mounts in my Falcon failed shortly after I got it and the engine moved enough that the fan hit the upper radiator nipple and the clutch arm fell out . I have seen an engine twisted around on its' side as a result of all the mounts failing combined with a heavy foot ; nothing quite like raising a hood and seeing an exhaust manifold where the air filter should be - not my car , thank goodness .

 

[dudeigota66]

Could it have been that the broken tranny mount and vibrating tranny loosened the motor mounts?

 

[oldgrezmonke]

Could it have been that the broken tranny mount and vibrating tranny loosened the motor mounts?

That has a very slim possibility ; a visual inspection for loose or missing motor mount nuts would quickly confirm or deny that .

 

[bubba22349]

As 69.5Mav said X2 for me, It's always the best practice (for me it's the only way) to replace all the mounts as a complete set this puts the engine and trans back in the right position so the linkage can work as designed too. I would also say that for safety you do need to fix this before you even try to drive the car again.