high idle.... help

not sure if im at the right place but here goes anyway. Ive got a manual 97 Mazda B4000 2wd. About a week ago I went to stop, everything was fine until I pressed the clutch, when I did the rpms shot up to 4000 and stayed there while I was at the light as soon as I put it in first and started to move the rpms went back to normal. the idle has dropped now to about 2000rpm and will sometimes jump between 1500 and 2000rpms but while driving it you cant tell anythings wrong, but as soon as you stop again the rpms hang around 2000 steady. I tested the idle air control valve and throttle position sensor both good well according to the multimeter anyways. the pcv valve has good suction but was oily. My throttle cable is tight and moving freely and the throttle plate was closed while the engine was idling and opens like it should. My throttle body is pretty dirty but not sure if its related. none of my research shows anything like this and I need my truck back for work and cant afford a mechanic. im leaning towards vacuum leaks, coolant sensor, spark plugs or a bad computer. Im kinda lost mechanically everything appears good but the idles stuck at 2000rpms

You might try cleaning the throttle body. I'd also post this question at fordranger.net because this website mostly deals with '82-'94 Mazda's, not re-badged Fords.

Your throttle cable should be slightly loose when closed. Do you have a check engine light? My experiences with Fords from this era is that any outside air that does not come through the mass airflow sensor causes the engine to run like a turd, even removing the oil cap when running does this. However, if your idle speed control motor or throttle plate was letting more air past, then it could cause this.

You might also want to try cleaning the mass air flow sensor. If it's a hot wire unit and it has gotten coated with dirt maybe it would fool the computer into a high idle condition.

posted at fordranger.net but I appreciate all of your help haven't had a chance to try anything yet but if any of yall have any more ideas please let me know thank you

just an update. I have installed a new IAC sensor. problem fixed. the idles fine the motors running smoother than ever and its shifting way better which I never mentioned but the high idle was making shifting almost impossible. however I don't understand that when unplug the IAC sensor the motor still idles like nothing happened and by my research it should die. but im not going to complain its running better than ever so im saying it's fixed. thank you all for all your help.