Intake Manifold

Modern manifolds are often plastic. Some have flaps or variable-length runners to improve torque. Sensors, the EGR inlet and vacuum hoses often connect to it. Variable intake systems change runner length to tune air flow for low-speed torque or high-speed power.

Air flows from the throttle body into a plenum and then through runners to the intake ports.

Leaking manifold gaskets cause vacuum leaks and lean codes. Stuck runner flaps can set fault codes and reduce performance. Carbon deposits from EGR and crankcase ventilation can build up in manifolds and restrict flow, especially on diesels.