Fuel Injected Engine

Fig. 60 EGR System.:

Fig. 63 EGR System.:

The EGR system, Figs. 51 through 63, is designed to reduce oxides of nitrogen emissions (NOx) by recirculating exhaust gasses through the EGR valve and the intake manifold into the combustion chamber. The system used on Accord with carbureted engines is composed of EGR valve, EGR control valves A and B, a thermovalve and on some models a check valve. The system used on Civic and CRX with carbureted engines except the 1986---87 federal and high altitude CRX HF is composed of EGR valve, EGR control valves A and B, EGR control switches, EGR control solenoid valves, control switch solenoid valve, vacuum switch, an electronic control unit, and on 1300 and HF models the speed sensor. The system used on 1986---87 federal and high altitude CRX HF includes manifold and atmospheric pressure sensors, coolant sensor, EGR valve with lift sensor, a constant vacuum generator and frequency solenoid valve, and an electronic control unit which monitors sensor outputs and engine and vehicle speed. The system used on Prelude with carbureted engines is composed of EGR valve, EGR control valves A and B, EGR control solenoid valve, thermosensor and vacuum switch. The system used on Accord and Prelude with fuel injected engines is composed of a EGR valve, CVC valve, EGR control solenoid valve, then fuel system ECU (Electronic Control Unit) and various sensors.
On models with carbureted engines, the EGR valve is operated by vacuum from the carburetor port and provides EGR volume proportional to engine loads by the operation of the EGR control valves A and B.
On models with fuel injected engines, the EGR valve is operated by vacuum from the intake manifold. When the EGR control solenoid valve opens, the EGR valve closes since vacuum is relieved into the intake manifold through the EGR control solenoid valve.
The EGR system recirculates exhaust gas only after the engine reaches normal operating temperature and then only while accelerating or cruising. EGR flow is cut off during idle, deceleration, and cold engine operation to assure good combustion during these conditions.