Exhaust Gas RECIRCULATION (EGR) System Test
NOTE:
EGR systems contain different components depending on application. See Figure. When testing EGR system and components, use proper illustration to determine component location.
NOTE:
When performing EGR system test, it may be necessary to monitor engine RPM by using scan tester. For scan tester connections, see IDLE SPEED & MIXTURE in ADJUSTMENTS
article.
- Ensure EGR vacuum modulator filter is clean and in good condition. Clean filter with compressed air (if necessary).NOTE: EGR vacuum modulator filter must be installed with coarse side facing upward, away from EGR vacuum modulator.
- Using "T" connector, install vacuum gauge in line with vacuum hose on top of EGR valve. Start engine. Ensure engine 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.
- Operate engine with engine coolant temperature less than minimum temperature and at specified engine RPM. See EGR TESTING SPECIFICATIONS table. No vacuum reading should be obtained.
- 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 at specified engine RPM. Ensure no vacuum is indicated at idle.
- Disconnect vacuum hose from port "R" of EGR vacuum modulator. See Fig 1. 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.
- Remove vacuum hose, vacuum gauge and reconnect original vacuum hoses. To check EGR valve operation, remove and plug vacuum hose located on top of 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. Shut engine off.
EGR TESTING SPECIFICATIONS
| Application Type | Minimum Temperature | Engine RPM |
|---|---|---|
| Tercel | 113°F (45°C) | 2500 |