EGR Vacuum Control System - Low Altitude

Fig. 001 EGR Vacuum Control System - Low Altitude (Same as Fig. 45, p. 13-18):

V8 LOW ALTITUDE (NA5) EGR SYSTEM

Vacuum from the vacuum pump is modulated by the Vacuum Regulator Valve mounted on the injection pump. Vacuum is highest at idle and decreases to zero at wide-open throttle. This variable vacuum then is sent to the Transmission Converter Clutch (Governor Pressure Switch) EGR (Dump) solenoid.
The TCC solenoid prevents vacuum from passing through, whenever both the transmission governor pressure switch and TCC cylinder head bolt temperature switch are closed. When the solenoid is energized, any vacuum present beyond the solenoid is vented through the "vented" port (1) of the solenoid.
When the solenoid is not energized, vacuum is then applied to port 3 of the EGR Thermostatic Vacuum Switch (EGR-TVS). The EGR-TVS is installed in a coolant passage of the intake manifold. It does two things; 1. its upper part is an electrical switch that energizes the HPCA and fast idle solenoids when coolant temperature is below 32°C (89°F). 2. its lower part is a vacuum switch that prevents vacuum from flowing to port 2 until 38°C ± 2° (100°F ± 3.6°) coolant temperature is reached. Below 32°C (89°F), vacuum cannot pass from port 3 to 2. Any vacuum that was present at port 2 is vented through port 1. Port 1 is blocked when ports 3 and 2 are connected.
Vacuum is then sent to both port 3 of the Altitude Solenoid and port 3 of the Vacuum Reducer Valve (VRV).
The Altitude (TRIM) Solenoid is energized by the EGR Altitude Sensing Control Switch at Altitudes above 1219 meters (4,000 ft.). When it is not energized, ports 2 and 3 are connected and port 1 is blocked. Therefore vacuum at ports 3 and 2 of the VRV are the same. This causes the vacuum at port 1 of the VRV to also be the same as the vacuum at port 2 and 3.
When the Altitude Solenoid is energized, ports 1 and 2 of the solenoid are connected and port 3 is blocked. Because port 1 of the Altitude Solenoid is a vent, port 2 of the VRV is open to atmospheric pressure. Now the VRV will regulate. The vacuum at port 1 of the VRV will then have a vacuum output 6.75 kPa (2.o" Hg.) lower than port 3 of the VRV.
Port 1 of the VRV is connected to port "S" of the Quick Vacuum Response (QVR) valve. When the vacuum applied to port "S" is constant or increasing, the vacuum output to the EGR valve will be the same as the input. When the vacuum input at port "S" drops, the vacuum in the EGR valve is vented through the vent opening of the QVR until the vacuum is the same. The QVR is an equalizing valve that reacts quickly.
The EGR valve is a vacuum modulated type. It should be fully open at 36 kPa (10.6" Hg.) and closed below 20 kPa (5.9" Hg.) VIN N