even when warm the engine will stay on fast idle and wont come off .You have to stop and hold the brake for about five seconds and then it will finally come down to the right idle.It is funny that it will not do this unless it is in gear then when you accelerate it stays up on a fast idle.I read the code on my scanner and it came back saying low voltage idle air control sensor which I did replace but didn't fix the problem .Any help would be greatly appreciated

 

There are several paths we can go here, so let's try this one first.
The vehicle's computer does not always know when a faulty part has been replaced , so whatever condition it has adapted to has to be told a change has been made.
The KAM ,Keep Alive Memory has to be erased and allowed to adapt to the new part.
To do this you will need to remove the negative battery cable from the battery and hold that cable end against the positive cable end for a few minutes until the memory is erased. This will also erase other things in the memory like radio stations , power seat settings etc. After the time has passed and the capacitors have discharged you can now reinstall the negative cable back on the negative battery post. Start the engine, BUT DO NOT TOUCH the throttle. Allow the engine to idle for a few minutes to relearn the new settings. This is one thing you can try and there are others, but we take them one at a time.