Exhaust Gas Recirculation: Testing and Inspection

Fig. 26 EGR Valve Vacuum Gauge Connection:

1. Start engine and connect vacuum gauge as shown in Fig. 26. Ensure engine runs properly at idle. If engine runs rough or stalls, check for improperly seated EGR valve.

Fig. 27 EGR Valve Vacuum Modulator Testing:

2. With coolant temperature below 104°F, run engine 3500 RPM and observe vacuum gauge. If gauge reading is not zero, Bi-Metal Vacuum Switching Valve (BVSV) is defective.
3. Warm engine to normal operating temperature and observe gauge reading at 3500 RPM. Gauge should indicate low vacuum.
4. Disconnect vacuum hose from port R of vacuum modulator and connect manifold vacuum directly to port R. Vacuum gauge should indicate high vacuum at 3500 RPM, Fig. 27
5 If improper readings are obtained in steps 3 and 4, check for defective vacuum modulator.
6. Remove vacuum gauge and adapter, reconnect proper vacuum hose to modulator, then apply manifold vacuum directly to EGR valve with engine idling.
7. If engine does not run rough or stall, EGR valve is defective.