I have a 1992 F150, 300 6cyl. I have a problem with a rough idle on initial start up, or after is has set and is cold. It smells EXTREMELY rich when it idles rough. On a 70 degree day, it will idle rough for approx. 10 seconds, and then smooth at immediately. On a 50 degree day, it may rough idle for 30 seconds, and on a 20 degree day, it may idle rough for several minutes. When it smooths out, it is like the flip of a switch....immediate. I replace the IAC, the computer, and one temp. sender.