Hyundai Accent acceleration problems

Well I told you, I had the problem that when my car left in neutral when I go along the road the car was stuck to 1500 rpm in the highs and in the traffic lights and I lowered very slowly how strange in which parking was parked even if I was on the light I did not accelerate it and it normally had to run it to see the problem I take it to the workshop
And the problem was arranged no longer staying and works well now. The problem arising to touch that screw was that when it turned on in the morning or that a long period off the revolutions fall to 500 and it goes out already heating does not give that problem now if it regulates it in cold to 1000 rpm it rises only up to 1500 and falls to 1000 This evil or the screw already has a leak and makes me pass more air from the devoid and that is why it is difficult for 1000 to have this car is that in cold it accelerated only in the morning so I changed the sensor by the advice of the mechanic but I do not solve the problem so I have spent almost 500 dollars in labor and sensors for nothing someone can give me an idea that it takes that screw internally I imagine that it will be an oring Cut the air or regulate it in some way like carburados