On an unmodified engine, intake manifold vacuum above 15" can indicate a mechanical problem.

Name: On an unmodified engine, intake manifold vacuum above 15" can indicate a mechanical problem.
Brand: Quizplus
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Question

Quizplus · Accepted Answer

In a healthy, unmodified engine, an intake manifold vacuum reading above 15 inches of mercury (inHg) at idle is typically a sign of normal operation, indicating good engine health and efficient combustion, not a mechanical problem.

On an Unmodified Engine, Intake Manifold Vacuum Above 15" Can