The IAC valve (Idle Air Control valve) is designed to keep a steady idle speed. The idle speed, also known simply as “idle,” is the amount of revolutions that the engine keeps when our foot is not pressing the accelerator. The IAC valve is controlled by the computer and it balances any burden upon the engine, like the usage of the air conditioner, the lights or the sound system. When the engine is cold, it helps it start by keeping the revolutions somewhat higher until the engine heats up.
⚠️ You should check the IAC valve periodically to make sure it is clean, since it usually malfunctions because of the accumulation of carbon residue which is produced by the combustion of the engine.