Why a high idle speed after changing the IAC?

A high idle speed after changing the Idle Air Control (IAC) valve may occur due to several factors. The new IAC might be malfunctioning, incorrectly calibrated, or not properly installed, leading to excessive airflow. Additionally, there could be vacuum leaks in the intake system or issues with other components like the throttle position sensor, which can also affect idle speed. It's essential to check for diagnostic trouble codes and inspect the entire intake system to identify the root cause.