To adjust the idle speed on a fuel-injected car, you'll need to locate the idle air control valve (IAC) and the idle speed adjustment screw. The IAC valve controls the amount of air entering the engine when the throttle is closed, while the idle speed adjustment screw determines the idle speed. Written By:- Alfredo Updated on September 10, 2023. To adjust the idle speed on a stihl chainsaw, locate the idle speed screw and turn it clockwise to increase the speed or counterclockwise to decrease it. Proper adjustment of the idle speed ensures smooth operation and prevents stalling. 5 Ways to Make Train Journeys More Fun. How Can I Adjust Idle Speed? Post by chobo2 » Sat Apr 29, 2017 8:03 pm. Hi. When my car is warmed up and I stop at a light or put it in "park" I get an idle speed of 600. This makes it kinda uncomfortable and I would like to correct. I am wondering if this is something I can adjust easily myself or if I need to bring it to a mechanic. Set idle speed adjusting screw, clockwise to increase rpm, counter-clockwise to decrease rpm. Idle rpm range should be 950 to 1050 rpms. Adjust idle mixture by turning idle mixture screw slowly clockwise until the engine runs poorly. Step 1. Start your car and allow it to cycle through at least one period of going through a higher RPM rate. This will ensure that the engine is completely warmed up and you will be able to adjust the idle properly. It is important to allow the engine to warm up because you will be driving your car mostly at that condition. Watching the tachometer shows an idle speed around 500 to 900 RPM. The engine's idle speed also changes, based on outside conditions. A computer is adjusting the idle speed, based on complex calculations. How do we adjust an engine's idle speed? In the past, adjusting an engine's idle speed was easy. Manufactures have removed these yuvdlhb.