I have a 1999 ranger with a 2.5 and tha mil came on reading P01506, Idle air control system overspeed error. Ive replaced the iac motor and theres no change... Evan a lil worse now. Ive swapped it with another new one thinking tha first was defective and no change!! My truck is a standard so imagine when you pull up to a red light and push tha clutch in your rpm jump up to about 2000-2500 untill you come to a compleat stop and then they drop around 1000. Thats what she does. A lil help would be muchly appreciated. Ty

 

did you replace the IAC gasket when you replaced the IAC? My truck (same year and engine) did the same and even after cleaning the IAC it did not get better. I replaced the gasket and the issue went away for the most part. It'll still hang around 1500 at times when its hot out but My truck naturally idles around 900-1100. Some tell me its high but when it idles any lower its real rough.

 

Oh and the gasket is less than 2$ at napa, when i called ford the parts guy argued with me that the truck didn't have a gasket there.

 

Yeah I replaced tha gasket. Yesturday I put the old one back on and its not that bad. I got tha new one from oreillys. I guess ima have to get one from tha dealer. Somethin bout thoes oreillys iac that my truck dont like