I need help to resolve this on going issue , everytime i start my legacy  (96 2.5 Eng)  RPM goes up to 4000 and slowly goes down below 1000. how can i adjust this issue????

Iac valve ,   clean or replace.

Thanks for your response, if i replace  the IAC will the ECU recognise it and adjust  the valve to its regular RPM. 

Yes,it will  but try a though cleaning first. It may not be your problem.  Does the car have any codes showing or pending?  

What ever you do do not try to adjust anything, it will only make it worse.   R&R only.  

first start - keep your foot off the gas pedal. If there's a 'zero' position being recorded, it should be accurate that way.