you could probably start buy cleaning the iacv. I am not sure if that is your issue or not but it is cheap and easy to do. the coolant temp sensor can mess with the idle also.
2004 Ext Cab, 4WD, 4.0, Auto, 146k. (4.0 engine is out of a 2009 Ranger w/96k) ( as of 3/10/2016)
2004 Ranger, Ext Cab, 2WD, 3.0, 5 speed , 4WABS, crank windows, no cruise, Edge 116k.(6/5,2014) (SOLD).
1999 Ford Ranger, Reg Cab, 2.5, 5 speed, 2WD, no AC, 150k (SOLD).