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Exhaust Gas RECIRCULATION (EGR) System Test

NOTE: EGR systems contain different components depending on application. See Fig 2. When testing EGR system and components, use proper illustration to determine component location.
NOTE: When performing EGR system test, it will be necessary to monitor engine RPM by using tachometer or scan tester depending on model application. For tachometer or scan tester connections, see IDLE SPEED & MIXTURE in the ADJUSTMENTS article.
  1. Ensure EGR vacuum modulator filter(s) are clean and in good condition. Clean filter(s) with compressed air (if necessary).
    NOTE: EGR vacuum modulator filter(s) must be installed with coarse side facing upward, away from EGR vacuum modulator.
  2. Using "T" connector, install vacuum gauge in line with vacuum hose on top of EGR valve. Start engine. Ensure engine runs idles smoothly to ensure proper seating of EGR valve.
    NOTE: The EGR system components can be checked with engine coolant temperature less than minimum temperature and engine at specified engine RPM.
  3. Operate engine with engine coolant temp. less than minimum temperature and at specified RPM. See the EGR TESTING SPECIFICATIONS  table. No vacuum reading should be obtained.
  4. Warm engine to normal operating temperature. Operate engine at specified engine RPM again. See EGR TESTING SPECIFICATIONS  table. Ensure a low vacuum reading is now obtained.
  5. Disconnect vacuum hose from port "R" of EGR vacuum modulator. See Fig 1.
  6. Using additional hose, connect port "R" of EGR vacuum modulator directly to intake manifold. High vacuum reading should be obtained at specified engine RPM. See EGR TESTING SPECIFICATIONS  table.
    NOTE: Engine should misfire due to large amounts of exhaust gas being injected into intake manifold.
  7. Remove vacuum hose and reconnect original vacuum hose to EGR vacuum modulator.
  8. On all models, to check EGR valve operation, remove and plug hose at EGR valve. Using vacuum pump, apply vacuum directly to EGR valve with engine idling. Engine should run rough or stall. If EGR system does not operate as described, each individual component should be tested.
Fig 1: Identifying Ports & Testing EGR Vacuum Modulator
G95A34439Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002
EGR TESTING SPECIFICATIONS

Application Minimum Temperature Engine RPM
Tercel 117°F (47°C) 2500
Fig 2: Identifying Emission System Components
G95H34451Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002
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