Exhaust Gas RECIRCULATION (EGR) System Test
NOTE:
EGR systems contain different components depending on application. See Fig 1. When testing EGR system and components, use proper illustration to determine component location.
NOTE:
When testing EGR vacuum modulator, it may 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 ADJUSTMENTS
article.
EGR TESTING SPECIFICATIONS
| Application | Minimum Temperature | Engine RPM |
|---|---|---|
| Supra | 122°F (50°C) | 3500 |
- 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.
- Using "T" connector, install vacuum gauge in line with vacuum hose at top of EGR valve. Start engine. Ensure engine runs idles smoothly to ensure proper seating of EGR valve.NOTE: The EGR system components are checked with engine coolant temperature less than minimum temperature and engine at specified engine RPM.
- Start and operate engine with engine coolant temperature less than minimum temperature and at specified RPM. See EGR TESTING SPECIFICATIONS table. No vacuum reading should be obtained. The EGR pipe should not be hot.
- 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.
- Using additional hose, connect port "R" of EGR vacuum modulator directly to intake manifold. High vacuum reading should be now 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 and reconnect original vacuum hose to EGR vacuum modulator. To check EGR valve operation, remove and plug hose at 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. Reconnect vacuum hose at EGR valve.