Examination
Models with carburetor engine
1. If you think the system is faulty, disconnect the hoses from the recirculation valve, back pressure valve and thermal vacuum valve and blow them out. If the hoses are not clogged, reconnect them.
2. The thermal vacuum valve testing operations are described in clause 2 of subsection 6.4.2.3.
3. To check the EGR valve, disconnect the vacuum hose from the top of the valve and connect another hose to the valve port. Pull air out of the hose; check that the valve diaphragm rises and quickly returns when you stop drawing air. The operation of the diaphragm can be checked by touching the underside of the valve with your finger, where you can feel the movement of the diaphragm. If the diaphragm moves with difficulty or does not move at all, the recirculation valve must be replaced.
4. If you are sure that the thermal vacuum valve is working properly, the backpressure valve can be checked as follows. Warm up the engine to normal operating temperature and disconnect the vacuum hose from the recirculation valve. Cover the hole of the disconnected hose with your finger and briefly increase the engine speed. When the engine speed (and exhaust gas pressure) increases, there should be a vacuum in the tube. When the engine speed drops, the vacuum in the hose should be stopped by the backpressure valve. If this is not the case, the valve is faulty and must be replaced.
All models with fuel injection system
5. The recirculation system can be checked as described in pp. 1–4, skipping the information regarding the thermal vacuum valve. Instead of the thermal vacuum valve, these models have a control solenoid valve. This solenoid valve is the same as the one that controls the operation of the fuel vapor control system and can be tested as described in paragraphs 2–5 of subsection 6.4.2.3.
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