Air Intake Hose
A flexible rubber or plastic duct that channels filtered air from the air filter box to the throttle body.
The air intake hose (also known as the air intake boot or duct) is a flexible conduit that connects the engine air filter housing to the throttle body. Its job is to route clean, filtered air into the intake manifold for combustion, while accommodating engine torque movement.
Air intake hoses are typically made of molded rubber or flexible plastic and feature pleated bellows sections to allow flex. Over time, the rubber can dry rot, crack, or tear, especially in the folds of the bellows. Clamps holding the hose can also loosen, allowing unfiltered air to enter the engine.
A tear in the intake hose after the Mass Air Flow (MAF) sensor allows 'unmetered air' to enter the engine. Because the ECU does not know this extra air is entering, the engine will run too lean, causing a rough idle, engine stalling, hesitating under acceleration, and check engine codes for lean fuel trim.