Nissan Micra EGR System Description & Vacuum Diagram - Carbureted Engine (EF & EC-24)

This is a page (EF & EC-24) from a factory service manual's Emission Control section, describing the E.G.R. (Exhaust Gas Recirculation) System on a carbureted engine. The text explains that the EGR system recirculates exhaust gases into the combustion chamber to lower combustion temperature and reduce NOx emissions. An EGR control valve meters exhaust gas flow from the exhaust manifold to the intake manifold using carburetor vacuum (via the E.G.R. VC port), and a thermal vacuum valve located between the vacuum passage and the EGR control valve keeps the system deactivated when engine coolant is cold to prevent poor engine stability. At idle or full throttle, the EGR control valve closes regardless of water temperature. Two schematic diagrams illustrate system operation: one with water temperature below 50°C (122°F), showing the EGR valve and thermal vacuum valve both closed, and one above 50°C (122°F), showing both open and exhaust gas flowing to the intake manifold. Callouts identify the carburetor, throttle valve, E.G.R. VC port, EGR valve, thermal vacuum valve, and exhaust/intake gas paths. Figure references SEC138 and SEC139 appear beside the diagrams. A reader learns how and when the EGR system activates on this carbureted application.