Technician A says an intake manifold vacuum leak may cause a high idle speed. Technician B says a dirty IAC bypass passage will not cause the idle speed to be below specifications. Who is correct?

Question

Quizplus · Accepted Answer

Technician A is correct because an intake manifold vacuum leak allows additional air to enter the engine, which can lead to a higher than normal idle speed. Technician B is incorrect because a dirty IAC (Idle Air Control) bypass passage can indeed cause the idle speed to be below specifications, as it restricts the air flow needed for proper idle operation.

Technician a Says an Intake Manifold Vacuum Leak May Cause