Exhaust Gas Recirculation: Testing and Inspection

Fig. 20 Exhaust Gas Recirculation System Operating Conditions:

1. Check system operating conditions, Fig. 20

Fig. 22 Vacuum Guage Connection:

2. Using a 3-way connector, connect a vacuum gauge to the hose between the EGR valve and vacuum pipe, Fig. 22
3. Check seating of EGR valve by starting the engine and check that the engine starts and runs at idle.
4. Check VSV with cold engine
a. The coolant temperature should be below 53° C (127° F).
b. Check that the vacuum gauge indicates zero at 2,500 rpm.
5. Check VSV and EGR vacuum modulator with hot engine.
a. Warm up the engine.
b. Check that the vacuum gauge indicates low vacuum at 2,500 rpm.
c. Check that the vacuum indicates zero at idle.

Fig. 23 VSV & EGR Vacuum Modulator Test:

d. Disconnect the vacuum hose from port R of the EGR vacuum modulator and connect port R directly to the intake manifold with another hose.
NOTE: As a large amount of EGR gas enters the engine will misfire slightly.
e. Check that the vacuum gauge indicates high vacuum at 2,500 rpm, Fig. 23
f. Remove the vacuum gauge and reconnect the vacuum hoses to the proper locations.
4. Check EGR valve.
a. Apply vacuum directly to the EGR valve with the engine idling.
b. Check that the engine runs rough or stops.
c. Reconnect the vacuum hoses to the proper location.

If no problem is found with this inspection, system is functioning; otherwise inspect each part.