If there are no CEL codes, disconnect the battery for a few hours and then re-connect.
Acceleration Cable broken broken, you dump!
Adjust the idle screw.
replace the alternator
sounds like it might be due to bad earthing. Check earth strap from battery to body to engine.
zyou tps might be bad
I wrote this question. Found a small rag jammed into the throttle body, obstructing the butterfly valve. WOW. Glad it didn't get sucked into a cylinder. And no, this was not my fault. I bought the car used and this is exactly how I found it when I yanked off the TB. Engine idles at proper speed now. A little rough at times, but I bet changing the 02 sensors will cure that.
On my Chevy truck it idles high when its low on antifreeze but if its not that more than likely its usually a vacuum line loose or cracked. good luck.
If the engine idles and revs up okay in neutral, it is likely the torque converter clutch lock up solenoid.
why does my 4.75 BRIGGS & STRATTON lawnmower engine idles high and low when cutting my grass
pull the negative side of the battery cable off and see if the engine dies. if not then with the negative battery off, have some one turn on every thing in the truck, if it still don't die then its your battery or maybe a regulator problem. i hope this helps, i have done this many times."depending on the alternator. some have the regulator built in to them""and dealing with the charging system always be careful and take your time"
Need a little more info. What Model and year of the vehicle?
Needs a Tune up