TESTING

EGR System and Valve

1. Start the engine and allow it to reach normal operating temperature.
2. Increase the engine speed to 3000–3500 rpm (no load). The valve shaft should move upward. On 1983–84 California, 2 wheel drive cars, the EGR system does not function until the engine has run for eight minutes.
3. Decrease speed to idle, the shaft should go down.
4. If the valve shaft fails to raise in Step 2, check the vacuum lines, connections, and the carburetor throttle vacuum port. Replace any clogged or damaged hoses, and clean the throttle port if it is clogged.
5. On 1974 models, connect the EGR vacuum hose directly to the carburetor throttle port. Speed the engine up and return it to idle as in Steps 2 and 3. If the valve works, the fault is in the vacuum solenoid valve or temperature switch.
6. If the EGR valve doesn't work:
   1. Remove the EGR valve from the intake manifold.
   2. Plug the vacuum inlet on the top of the valve diaphragm.
   3. Depress and release the diaphragm several times.
   4. The diaphragm should remain depressed while the vacuum inlet is plugged. If not, the diaphragm is leaking and the valve must be replaced.
   5. If the valve stem seems stuck, clean the diaphragm with a wire brush or spark plug cleaner (NOT solvents).
   6. Install the valve and test it again. If it still does not work, replace it.

VACUUM SOLENOID VALVE AND COOLANT TEMPERATURE SWITCH (1974 ONLY)

1. Disconnect the vacuum solenoid leads.
2. Connect the solenoid directly to a 12 volt power source. The solenoid should click on. Disconnect the solenoid, it should go off. If not, it is defective. Replace it and perform the system test again.
3. If the solenoid is working properly and everything else in the system is in proper operating order, replace the coolant temperature switch, then perform the system tests again.

THERMAL VACUUM VALVE (1982–84)

This valve actuates both vacuum spark advance and the EGR valve. It turns the EGR valve off until the engine is warmed up to help ensure smooth cold engine performance.

Drain some coolant out of the system, disconnect the vacuum hoses, and remove the valve from the intake manifold.

CAUTION
When draining coolant, keep in mind that cats and dogs are attracted by ethylene glycol antifreeze, and are quite likely to drink any that is left in an uncovered container or in puddles on the ground. This will prove fatal in sufficient quantity. Always drain coolant into a sealable container. Coolant should be reused unless it is contaminated or several years old.

Cap off the top (air cleaner) port and install hoses on the other two ports (to keep the top of the valve dry). Then, immerse the valve in cool water. Use a thermometer to measure water temperature. Blow into either hose and warm the water (for example, on a stove). The valve must open when water rises past 68°F (20°C). Now, remove the water from heat and chill with ice cubes. The valve must close as the temperature drops below 50°F (10°C). If not, replace the valve.