Exhaust Gas Recirculation: Description and Operation

Fig. 39 Egr Valve Location, 16V (California):

California vehicles with the 2.0 liter 16 valve engine, are equipped with an EGR system. The EGR system is designed to reduce NOx emissions.
The three major components used in the EGR system are the:
EGR valve
Vacuum amplifier
Vacuum thermo-switch

The EGR valve is located on the back of the intake manifold, Fig. 39. The function of the EGR valve is to control the amount of exhaust gas returned to the combustion chamber to reduce the peak combustion temperature.
By reducing the peak combustion temperature, the formation of oxides of nitrogen (NOx) is reduced.

Fig. 37 Vacuum Amplifier, 16V (California):

The EGR valve is opened be intake manifold vacuum via the vacuum amplifier, Fig. 37. The purpose of the vacuum amplifier is to supply vacuum to the EGR valve during acceleration (low manifold vacuum).

Fig. 35 Vacuum Hose Diagram, 16V (California):

The vacuum amplifier receives two vacuum inputs, Fig. 35. The primary input is directly from the intake manifold and the secondary input is from the throttle body before the throttle plates.
When the vacuum inputs are equal, such as during wide open throttle, the EGR valve will close, allowing peak engine performance.

Fig. 38 Vacuum Thermo-switch, 16V (California):

A thermo-pneumatic valve, Fig. 38, is installed in the primary vacuum supply line to the vacuum amplifier. This valve will open and allow the EGR valve to operate when the coolant temperature reaches approximately 50°C (122°F). The valve will close when the coolant temperature is below approximately 27°C (81°F).

Fig. 39 Egr Valve Location, 16V (California):

An EGR temperature sensor is located in the intake manifold near the EGR valve, Fig. 39. It is used to inform the CIS-E Motronic control unit if the EGR system is functioning properly.
The sensor is used to measure the temperature of the recirculated exhaust gas coming from the valve. This sensor is a malfunction detection sensor only.
If the EGR valve, temperature sensor or wiring fails, the fault is stored in the CIS-E motronic's permanent fault memory, and also illuminates the "CHECK" light which is located to the right of the instrument panel.
All emissions related faults will be stored in the CIS-E Motronic's fault memory, and on California vehicles, the engine "CHECK" light to the right of the instrument panel will illuminate if a fault exists.