I have a 2002 f150 4.6 I changed the idle control motor now the idle is erratic won't return to a normal idle for several seconds, did I miss something, if I plug it runs fine till a/c or cold start then it has trouble.

 

Didn't realise the IAC unit contained a motor. I thought it was merely a solenoid controlled valve.

Anyhoo, I'm no grease monkey but erratic idle might be due to something as simple as a fouled fuel filter. Or perhaps a faulty O2 or MAF sensor, both of which are easy fixes.

Start by plugging in an ODB code reader and see if any errors show up.