4 weeks ago

1999 ford expedition 5.4. The truck kept stalling every time I stopped at a light. Other then that it drove perfect. I changed the air idle control valve now it doesn`t stall but when I start it the idle is almost at 2k then levels off at about 900. Then after a few minutes of driving it goes down to about 500 and feels like it going to stall but doesn`t. Any ideas?