System Diagnosis

Fig. 13 Checking movement of EGR valve diaphragm:

EXHAUST GAS RECIRCULATION (EGR) SYSTEM CHECK
1. With engine running and coolant temperature below 113°F (45°C), check that EGR valve is not open by feeling diaphragm.
2. Allow engine to reach normal operating temperature. Race engine and check that diaphragm moves toward 1, Fig. 13, during acceleration and toward 2 during deceleration.

Fig. 14 Checking bi-metal vacuum switching valve low temperature operation:

Fig. 15 Checking bi-metal vacuum switching valve high temperature operation:

BI-METAL VACUUM SWITCHING VALVE (BVSV) CHECK
1. With engine cold, drain cooling system.
2. Remove BVSV from intake manifold.
3. With BVSV below 113°F (45°C), blow air into each nozzle individually, Fig 14. Air should escape from filter.
4. With BVSV heated above 140°F (60°C) in hot water, blow air into each nozzle individually, Fig. 15. Air should not escape from filter.
5. Wrap sealing tape around threads and reinstall BVSV in intake manifold.
6. Reconnect vacuum hoses.

Fig. 16 EGR modulator. Exploded view:

Fig. 17 Testing EGR modulator:

Fig. 18 High speed EGR modulator test:

EGR MODULATOR
1. Inspect filter for dirt or damage, Fig. 16. Clean filter using compressed air.
2. With engine off, disconnect 2 vacuum hoses from EGR modulator and plug nozzle. Blow air into other nozzle and check that air escapes freely through filter, Fig. 17.
3. Start engine and allow to reach normal operating temperature.
4. Increase engine speed to 5000 RPM and plug one nozzle of modulator. Blow air into other nozzle. Strong resistance to air flow should be felt, Fig. 18.
5. Reconnect vacuum hoses.




EGR VALVE
1. Remove EGR valve and inspect for sticking or exhaust deposits.
2. Reinstall EGR valve with new gasket.
3. Reconnect vacuum hoses.