EGR Functional Tests
The complete EGR system should be inspected and tested at the time intervals recommended by the manufacturer. To assure proper operation of this system all passages and moving parts must operate properly free of deposits, also hoses and connections must be free from leaks. Ambient temperature in the area of the vehicle must be above 68° F for this test.
Warm up engine and allow the engine to idle, in neutral, with the carburetor throttle closed; then abruptly accelerate the engine to approximately 2000 RPM, but not over 3000 RPM. Visible movement of the EGR valve stem should occur during this operation. This can be determined by change in the relative position of the groove on the EGR valve stem. This operation should be repeated several times to confirm movement. Movement of the stem indicates that the control system is functioning correctly.
If control system is functioning properly, the valve and passages may be checked for exhaust gas flow by applying a vacuum of at least 10 inches Hg directly to the EGR control valve with the engine warm and idling in neutral. Idle speed should drop 150 RPM or more when vacuum is applied. This reduction in idle speed confirms that exhaust gas recirculation is taking place. If the speed change does not occur, or is less than that specified, exhaust deposits in the EGR valve or intake manifold EGR passages are indicated.
Turbocharged 4-135/2.2L Engines
To assure proper operation of back pressure EGR system, all passages and moving parts must be free of clogging or sticking as a result of deposits. The entire system should be free of leaks. Any vacuum lines or components found to be leaking should be replaced.
Inspect all vacuum line connections between the throttle body, EGR control valve and back pressure transducer. Replace any split or otherwise damaged vacuum lines or connectors.
The EGR valve stem is not visible on 4-135/2.2L turbo EGR valves. Therefore, it is necessary to proceed as follows to verify system operation.
1. Disconnect vacuum hose from EGR valve and connect suitable vacuum gauge, then start engine and accelerate to 2000 RPM. With engine temperature below 90°F, vacuum gauge should show a steady reading of zero. If so, proceed to step 2. If gauge shows an unsteady reading above zero, replace EGR solenoid.
2. Disconnect vacuum line to EGR back pressure transducer from EGR solenoid. Connect a vacuum gauge to this line, then start engine and wait until sufficiently warm for solenoid to open, then raise engine speed to 2000 RPM. If gauge reads at least 5 inches Hg vacuum, proceed to step 3. If gauge does not read at least 5 inches Hg of vacuum, repair vacuum supply from throttle body and solenoid, then disconnect vacuum gauge from vacuum line and reconnect vacuum line to EGR back pressure transducer.
3. Disconnect vacuum line to EGR valve vacuum motor from EGR back pressure transducer and connect a suitable vacuum gauge to this line, then start engine and raise engine speed to 2000 RPM. If vacuum gauge reads approximately 5 inches Hg vacuum, proceed to step 4. If vacuum gauge does not read approximately 5 inches Hg vacuum, replace EGR valve/back pressure transducer assembly.
4. Connect an auxiliary vacuum supply to EGR valve vacuum motor and, with engine running at idle speed, slowly apply vacuum. If engine speed begins to drop when applied vacuum reaches 2.0 - 3.5 inches Hg vacuum, proceed to step 5. If engine speed does not drop, replace EGR valve/back pressure transducer assembly, then repeat step 4. Before replacing assembly, check for clogged EGR supply tube or passages.
5. With engine set up as in step 4, apply 10 inches Hg vacuum. If vacuum holds without bleeding for 10 seconds, system is satisfactory. If vacuum does not hold, replace EGR valve/back pressure transducer assembly.