The idle speed on fuel injected engines is electronically controlled by the Engine Control Module (ECM) computer. The Idle Speed Control (ISC) system electrically oversees the proper idle speed for all operating conditions. There are no adjustments possible with this system. Any roughness or uneven idle is almost always due to other causes such as a clogged injector, air leak or loose, corroded terminals in the wiring harness, etc.
Idle speed is maintained by the Engine Control Unit (ECU). No adjustment is necessary or possible.