ASE Advanced Engine Performance Specialist (L1) Practice Test 2025 – The Complete All-in-One Guide to Achieve Certification Success!

A high Idle Air Control (IAC) can indeed be influenced by several factors, which is why the most comprehensive answer captures all possible causes, including throttle body contamination, clogged IAC passages, and a faulty IAC.

When the throttle body is contaminated, it may not allow for proper airflow regulation, leading to an abnormal increase in air entering the intake manifold. This could create an overly high idle condition as the engine management system attempts to compensate for the changes.

Clogged IAC passages inhibit the ability of the IAC valve to control airflow effectively. This blockage can prevent the valve from opening or closing according to the engine control unit's demands, which might result in unregulated air entering the engine and, consequently, a high idle.

Additionally, a faulty IAC itself, whether due to electronic malfunction or mechanical failure, can lead to improper functioning. If the IAC is stuck open or does not respond accurately to control signals, it would allow more air into the engine at idle, resulting in a higher-than-normal idle speed.

By considering these various potential causes together, it becomes evident how the correct response encompasses all three factors, providing a complete understanding of what might lead to a high Idle Air Control condition.