1987 (EGR) Systems - Functional Diagnosis

1987

6-11
Exhaust Gas Recirculation (EGR) Systems


Functional Diagnosis



PORTED EGR VALVE
1. Make certain that all vacuum hoses are correctly routed and securely attached. Replace cracked, crimped or broken hoses.

2. Make certain there is no vacuum to the EGR valve at idle with the engine at normal operating temperature.

3. Install a tachometer, Rotunda 059-00010 or equivalent.

4. Disconnect the Idle Air Bypass Valve (9F715) electrical connector (EFI engines only).

5. Remove the vacuum supply hose from the EGR valve nipple. Plug the hose.

6. Start engine, idle with transmission in NEUTRAL, and observe the engine idle speed. If necessary, adjust idle speed according to Section 4.

7. Slowly apply 5-10 inches of mercury vacuum to the EGR valve vacuum nipple using a hand vacuum pump, Rotunda 021-00014 or equivalent.

8. When vacuum is applied to the EGR valve and any of the following occur, replace the valve:

^ Engine does not stall.

^ Idle speed does not drop more than 100 rpm.

^ Idle speed does not return to normal (+/- 25 rpm) after the vacuum is removed.

9. Reconnect the idle air bypass valve electrical connector.

10. Unplug and reconnect the EGR vacuum supply hose.

11. The EGR system is OK, refer to the Diagnostic Routines in Section 2.
1987
6-12 Exhaust Gas Recirculation (EGR) Systems


Functional Diagnosis




ELECTRONIC EGR (EEGR) VALVE
1. Make certain that all vacuum hoses are correctly routed and securely attached. Replace cracked, crimped or broken hoses.

2. Make certain there is no vacuum to the EGR valve at idle with the engine at normal operating temperature.

3. Install a tachometer, Rotunda 059-00010 or equivalent.

4. Disconnect the Idle Air Bypass Valve (9F715) electrical connector (EFI engines only).

5. Remove the vacuum supply hose from the EGR valve nipple. Plug the hose.

6. Disconnect the 9G428 EVP sensor electrical connector mounted on top of the 9H473 valve.

7. Start engine, idle with transmission in NEUTRAL, and observe the engine idle speed. If necessary, adjust idle speed according to Section 4.

8. Slowly apply 5-10 inches of mercury vacuum to the EGR valve vacuum nipple using a hand vacuum pump, Rotunda 021-00014 or equivalent.

9. When vacuum is applied to the EGR valve and any of the following occur, replace the valve:

^ Engine does not stall.

^ Idle speed does not drop more than 100 rpm.

^ Idle speed does not return to normal (+/- 25 rpm) after the vacuum is removed.

10. Reconnect the idle air bypass valve electrical connector.

11. Unplug and reconnect the EGR vacuum supply hose.

12. Reconnect the EVP sensor electrical connector.

13. The EGR valve is OK, REPLACE EVP sensor if the Continuous Code 32 was present. If the Continous Code 32 was not present, refer to the Diagnostic Routines in Section 2.