I have tried playing with screw that controls throttle plate it does work at first allowing to reach 1200 rpm at idle however after stopping car and starting again it does go down to ~600rpm again like computer adjusts it back to desired level. There's also **** on Idle valve however turning it does nothing.

Is there way to reprogram computer to make 1200 a desired RPM?

Like try this yourself reach about 1200 rpm and then hold your leg still not looking at the rpm your once you hold it for a while it goes down to normal rpm, only way to hold constant 1200 RPM is to play with gas pedal.

P.S. I want to raise RPM to avoid misfire.

 

RPM is not adjustable ! Controlled by the computer.
Why not determine the cause of the misfire unless you already know !
Simple thing like a vacuum leak can produce misfire at idle, unfortunately so can a valve problem.

 

i checked vacuum leak fuel pressure done injector cleaning 3 times and nothing helps must be head gasket or cracked head, i will drive it until it stalls then tow it home with AAA and swap engine when time comes.

Its on me what type of solution in implement i still looking for how to adjust idle if you got info please share.

This info is totally incorrect then? http://www.explorerforum.com/forums/...cedure.262930/


How much does it cost to override idle speed in computer?

 

The site you referred to is someone doing something with a perfectly running engine.
Your vehicle evidently has a problem that you are trying to mask by attempting to adjust the idle speed. If you choose to do that, fine, let us know if that works for you since it might and might not.