Exhaust Gas Recirculation: Testing and Inspection

Back Pressure Variable Transducer (BVT) Schematic Diagram:

BACK PRESSURE VARIABLE TRANSDUCER (BVT) SYSTEM
1. Verify that all vacuum hoses are routed correctly and securely attached. Replace crimped, cracked, or broken hoses.
2. With the engine at normal operating temperature, make certain there is no vacuum to the EGR valve at idle.
3. Install a tachometer.
4. Disconnect the Idle Air Bypass Valve electrical connector (EFI engines only).
5. From the EGR valve nipple remove the vacuum supply hose, then plug those.
6. Start engine, while at idle in neutral, observe engine idle speed. If necessary, adjust idle speed.
7. Using a hand vacuum pump, slowly apply 5-10 inches of mercury vacuum to the EGR valve vacuum nipple.
8. When vacuum is fully applied to the EGR valve:
If engine stalls or if idle speed drops more than 100 rpm, perform the next step. Otherwise, replace the valve for vacuum leak at EGR valve.
If there is any EGR passages are blocked, clean the valve using EGR valve cleaner.
Remove the vacuum from the EGR valve. If idle speed does not return to normal (+/- 25 rpm), check for contamination, clean the valve.
If symptom still exists, replace the EGR valve.
9. Connect the idle air bypass valve electrical connector.
10. Unplug and reconnect the EGR vacuum supply hose.
11. Disconnect the vacuum connection at the Back Pressure Variable Transducer (BVT 9J431).
12. Gently blow into the hose to Port C until the relief valve closes, while applying 5-10 inches of mercury vacuum to Port E with a hand vacuum pump. Port E should hold vacuum as long as there is pressure on Port C.
13. Using a hand vacuum pump apply a minimum of 5-10 inches of mercury vacuum to Ports B and C. Ports B and C should hold vacuum.
14. If any of the Ports do not hold vacuum, replace the BVT.
15. Reconnect the vacuum at the BVT.
16. If neither the EGR valve nor the BVT were replace, the system is ok.