1990 Ranger 2.9L
I was having some rev hang when letting off the throttle, I don't have any linkage issues, I checked for vacuum leaks but none, so I turned to the Idle air control valve next.
I would like to just replace it since the parts not expensive, but when I put the new one in my truck starts idling at 2k RPM. I disconnected my battery to reset the ECU hoping that would fix the issue but nope. When I unplug the cable for the IAC valve the idle goes to like 400 RPM and I gotta tap the gas to keep it alive which is expected.
To me that indicates the issue is not with any vacuum leak but has something to do with my new IAC valve.
I would like to know what brand IAC valve do you have in yours if not OEM? Is there something I need to do to adjust my ECU to the new IAC?

For now, I just cleaned the old one out and put it back in until I can figure it out. Can't find anything in my Hanes manual or online.

 

warm up motor to running temp. unplug IAC and see what happens. if motor stalls or idles ruff IAC is working;

 

Yea, i did take off the old one and clean out the carbon deposits with brake clean, and now it works again just fine. I would still like to know in the future when I do need to replace it one day if I'm just using the wrong brand of part or if there's some sort of ECU reprogram operation i need to do to get it accustomed to the new IAC

 

most factory parts, sensors last a long time. people start replacing parts unnecessarily because the havent found the problem. most of the replacement parts now come from china untested. but they will replace it free. . best to test all parts before replacing them.