What are the symptoms of an intake manifold air leak?

[MacEverly]

When there is an air leak in the intake manifold, the following symptoms may occur: 1. Engine power loss: Since the air entering the engine through the intake manifold crack bypasses the air flow sensor, this unmeasured air dilutes the combustible air-fuel mixture in the engine cylinders, resulting in reduced engine power. 2. Increased nitrogen oxide (NOx) emissions: Since nitrogen oxides in vehicle exhaust are formed under high-temperature, oxygen-rich conditions, an excessively lean air-fuel mixture further promotes NOx formation, thereby increasing tailpipe pollutant emissions. 3. Hard starting: As the engine requires a richer air-fuel mixture during startup, the lean mixture caused by intake manifold leakage may lead to difficult engine starting.