System Diagnosis
EGR System TestCOLD ENGINE
NOTE: The engine coolant temperature must be below the thermovalve A set temperature (55°C, 131°F).
Setup For Test Condition 3:
1. Disconnect the vacuum hose from the EGR valve and connect a vacuum gauge to the hose.
2. Start the engine and raise the engine speed to 3,000 rpm.
Vacuum should not be available.
- If vacuum is not available, go on to the hot engine inspection (right column).
- If vacuum is available, replace thermovalve A and retest.
HOT ENGINE
1. Disconnect the vacuum hose from the EGR valve and connect a vacuum gauge to the hose.
2. Start the engine and wait for the cooling fan to come on.
3. Remove the control box from the firewall by removing the two bolts, then remove the control box cover by removing the four screws.
Vacuum should be as shown
- If vacuum is available at idle (condition 1) check the vacuum hoses for proper routing and connections, then check for correct idle speed and idle mixture, and make adjustment as necessary.
- If there is no vacuum in conditions 2 and 4, check the thermovalve A.
Disconnect the # 18 vacuum hose from the thermovalve A. Check for vacuum at the # 18 hose.
- If there is no vacuum, check the routing for the #18 vacuum hose and repair or replace as necessary.
- If there is vacuum, replace the thermovalve A and retest.
Setup For Test Condition 3:
- If vacuum is more than 2" Hg in condition 3, replace the EGR control valve and check the vacuum hoses for proper routing and connections.