In neutral while tapping the gas up to 12 then back to idle at 8 a couple time its fine then it will stay at 12. tap it again then it goes up to 20 and stays. i pull back on the petal and it doesn't do anything. hit it again and it takes off and i have to turn the car off. any advice would be great. thanks

 

Lack of lubrication of throttle cable and other moving parts, or a weak throttle return spring unable to overcome friction in throttle cable, or both in combination

 

You may want to remove it and give it a good cleaning as well. Perhaps just dirty and sticking.