Metro L3-61 1.0L (1990)
EGR Electronic Vacuum Regulator Solenoid: Description and Operation
The EGR is controlled by the ECM through an EGR vacuum switching valve (EGR VSV) and modulator. Vacuum is allowed to the EGR Valve at
acceleration and shut "OFF" upon deceleration or constant engine speed. The diaphragm mounted in the EGR modulator is operated by back pressure of
the exhaust gas to open and close the EGR VSV. By this opening and closing action of the EGR VSV, the EGR modulator controls the vacuum
transmitted to the EGR valve. Under a low load condition such as low speed driving, the exhaust pressure is low. In this state, the diaphragm in the EGR
modulator is pushed down by the spring force and the modulator valve opens to allow the air into the vacuum passage from the outside. As a result, the
vacuum transmitted to the EGR valve becomes smaller and so does the opening of the EGR valve. Thus, less amount of exhaust gas is recirculated to the
intake manifold.
Under a high load condition such as high speed driving, on the other hand, the exhaust pressure is high. By the high exhaust pressure, the diaphragm in
the modulator is pushed up and closes its valve. As the air does not enter the vacuum passage in this state, the vacuum transmitted to the EGR valve
grows larger and so does the opening of the EGR valve. Thus, larger amounts of exhaust gas is recirculated to the intake manifold. Under any one of the
following conditions, the ECM closes the vacuum passage of the EGR VSV and the EGR valve remains closed:
^
When engine coolant temperature is low.
^
When throttle valve is at idle position.
^
When engine is running under high load.
When intake manifold pressure is low. Other than the above, the EGR valve opens and closes in accordance with the EGR modulator operation.
