Any suggestions would be greatly apprecited. My 2000 Ranger (~61K miles) has a rough idle when warm. I can smooth out the idle by increasing the engine load (i.e. A/C, etc...) I have given it a tune up (air filter, plugs, ignition wires). I have an OBDII scanner that I attach to my computer, but I see nothing really wrong (not that I'm great at reading it yet. Does anyone have any suggestions please.

fuel filter

probably a vacuum leak somewhere

Did the OBD II indicate any code at all? If there is a problem, it should indicate an alpha-numeric like P0174 or P0203, etc. The PCM runs on default setting until the engine warms up so it could caused by any of the inputs such as 02 sensor, temperature sensor, vaccum sensor, etc. Before you spend anymore money replacing components, if stumped, have it checked with diagnostic equipment. That will pinpoint exactly what's ailing it and recommend the proper procedure to correct it.

My Ranger is an 03 with 27000 miles on it and no codes are present.

ford is good for the air idle control going bad or just getting dirty, check the PCV valve, make sure the ball moves inside, pull it out with the truck is running and stick your finger on it to make sure there is vacuum. try whatever you can where you don't have to keep blowing your money

Have you checked the egr yet? The easiest way is to disconect the vac line to the egr with the vehicle idling and use a vacuum pump (or a length of vac hose and suck on it) to apply vacuum to the egr the engine should stumble or completely die. if it doesn't then the egr is prob stuck, if it's stuck alittle open that could cause a rough idle. If its stuck you can pull it off and clean it or replace it. good luck