Exhaust Gas RECIRCULATION: Testing: Notes

With engine at normal operating temperature, install a tachometer and a vacuum gauge to intake manifold. Attach a second vacuum gauge with a "T" fitting between low temperature vacuum control valve and EGR valve.
Start engine and disconnect throttle stop solenoid wire (or depress solenoid plunger) to allow engine to operate at low idle speed. Observe reading on vacuum gauge at EGR valve. Vacuum reading should be less than 1.8 in. Hg. If vacuum reading is greater than 1.8 in. Hg; replace carburetor and recheck vacuum reading (Federal) or replace vacuum amplifier and recheck vacuum reading (Calif.). Shut off engine.
Open throttle and move choke valve to full choke position. Holding choke plate closed, close throttle. This will hold fast idle position. Disconnect and plug vacuum hose from EGR valve. Start engine and allow it to stabilize. Observe and record tachometer and intake manifold readings. Reconnect vacuum hose to EGR valve; allow engine speed to stabilize and again observe and record tachometer and intake manifold readings. If engine speed and manifold vacuum drop, EGR system is operating properly. Engine speed should drop at least 100 RPM. If engine speed and intake manifold vacuum reading does not change when hose is reconnected to EGR valve, EGR system is not functioning.