Engine reving up to 2000rpm on its own then droping to 300rmp.

[Jmacfarlane]

Just had my 2014 fiesta st 1.6L baby go nuts. I stop at a light and the rpms took off from a normal idle to 2000 rpms. I gave it a shot of gas to see if it would drop down which it did but then continued to drop below a normal idle. Then climb back up on its own to over 2000rpms. Was trying to rush back home incase it broke down on me and then lost all power. I could push the gas pedal all the way down but it would bairly move engine light came on of course. I pulled off the road and while sitting there idleing it was racing up and then would drop to almost stall out.
I shut it off and restarted the car and it was ok for about 3 mins then started doing it all over again.
Anyone have any ideas????

 

[frankiefiesta]

Able to read the code? From the CEL

 

[Drunkun_Munky]

Take off the big air box on the top of the engine and buried below you will find a pipe that is for air flow, they have a common tendency to split, I had the same problem with mine. If you have some brake cleaner, spray it around the engine behind the throttle body, if the engine drops revs then you have an air leak.

 

[Jmacfarlane]

Dont have a code reader with me

 

[Jmacfarlane]

And Ill check the pipe for a split

 

[Hijinx]

Take off the big air box on the top of the engine and buried below you will find a pipe that is for air flow, they have a common tendency to split, I had the same problem with mine. If you have some brake cleaner, spray it around the engine behind the throttle body, if the engine drops revs then you have an air leak.

I think maybe you're not in quite the right place...

Anyway, OP do you have an oil catch can?




Some Guy On The Internet

 

[Drunkun_Munky]

If I remember rightly its under the inlet manifold, quite hard to find but the brake cleaner helps a hell of a lot.

 

[Hijinx]

If I remember rightly its under the inlet manifold, quite hard to find but the brake cleaner helps a hell of a lot.

Ah ok... I had to give another read to what you wrote. I'm on the same page with you now.


Some Guy On The Internet

 

[Jmacfarlane]

At my gf's place dont have anything with me ... of course

 

[Jmacfarlane]

Ok just looked couldnt find anything wrong with any of the hoses but i took it for a drive up the street and what happend was, the rpms start bouncing and the is no reponce at all from the gas pedal. I can mat it to the floor but has no effect at all. This is causing the car to keep lurching cause its not allowing for any acceleration.

 

[Drunkun_Munky]

Could be your throttle position sensor or even throttle body it's self, try giving it a good clean out. if it was any of them though I would of thought they would throw up a code.

 

[Jmacfarlane]

Both the check engine light and the wrench ligh comes on

 

[frankiefiesta]

I'm guessing you don't have a Cobb accessport? You could check codes with that

 

[nmh5001]

I was going to say vacuum leak, cause the RPM thing sounds similar to what happened in my Subaru, but flooring it still gave me power. Weird.

 

[LaserWhisperer]

Any modifications recently installed?

 

[Jmacfarlane]

Update cars all fixed had to have the throttle assembly totally replaced. Works fine now or atleast for the hour drive home. Took 3 days to get the parts in.