System Operation
When the engine is idling below 1300 RPM (automatic transmission) or 1500 RPM (manual transmission), the speed sensor on the flywheel housing monitors engine RPM and relays this information to the ECB. No EGR occurs. The thermocontact prevents any EGR until the coolant temperature is above 118°F (48°C).
When the engine reaches 1300 RPM (automatic transmission) or 1500 RPM (manual transmission) and temperature is above 118°F (48°C), the ECB opens the electrovalve. The vacuum is at its peak and opens the EGR valve to maximum position. Maximum EGR occurs.
At engine speeds between 1300 RPM (automatic transmission) or 1500 RPM (manual transmission) and 3100 RPM, the amount of EGR decreases as the engine speed increases. At engine speeds above 3100 RPM, the electrovalve closes and no vacuum is applied to the EGR valve, no EGR occurs.