Emission Control Systems: Testing and Inspection

Cold Engine

1. Check vacuum line for proper connection, cracks, blockage or disconnected hose.
2. Disconnect No. 3 vacuum hose at purge control diaphragm valve and connect vacuum gauge to hose.
3. Start engine and allow to idle. Engine coolant temperature must be below 131°F on Accord or below 158°F on Prelude. Vacuum should not be available.
4. If there is vacuum, replace thermovalve and repeat test.

Hot Engine

1. Disconnect No. 3 vacuum hose at purge control diaphragm valve and connect vacuum gauge to hose.
2. Start engine and warm to normal operating temperature.
3. If there is no vacuum at idle, replace thermovalve and repeat test.
4. Disconnect vacuum gauge and reconnect hose, then remove fuel filler cap.
5. Remove canister purge air hose from frame and connect hose to vacuum gauge.
6. Raise engine speed to 3500 RPM. Vacuum should appear on gauge within one minute.
7. If there is no vacuum, disconnect vacuum gauge and install fuel filler cap.
8. Remove charcoal canister and inspect for damage or defects, replacing as necessary.
9. Stop engine and disconnect No. 3 vacuum hose from canister PCV fitting, then connect vacuum pump to canister PURGE fitting and apply vacuum. Vacuum should remain steady.
10. If vacuum drops, replace canister and repeat test.
11. Restart engine and reconnect hose to canister PCV fitting. PURGE side vacuum should drop to zero. If not, replace canister and repeat test.