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Test NTC-18A - Checking EGR System

NOTE: Perform TEST TC-118A - FUEL SYSTEM RICH  or TEST NTC-17A - CHECKING EVAPORATIVE EMISSION SYSTEM  before proceeding.
  1. Ensure ignition is off. Disconnect vacuum supply hose at EGR solenoid. The EGR solenoid is located on top of EGR backpressure transducer which contains vacuum hose to EGR valve. See Fig 1.
    Fig 1: Locating Typical EGR Solenoid & Components
    G98G00642
  2. Install vacuum gauge on disconnected vacuum supply hose. Start engine. If vacuum is 10 in. Hg or less at idle, go to next step. If vacuum is more than 10 in. Hg at idle, go to step  5.
  3. Turn engine off. Disconnect vacuum supply hose for EGR solenoid at intake manifold. Install vacuum gauge on vacuum supply hose port on intake manifold.
  4. Start engine and note vacuum reading with engine idling. If vacuum is more than 10 in. Hg at idle, repair restriction or leak in vacuum supply hose to EGR solenoid. Perform TEST VER-2A - ROAD TEST VERIFICATION . If vacuum is 10 in. Hg or less at idle, repair plugged vacuum port on intake manifold. Perform TEST VER-2A - ROAD TEST VERIFICATION .
  5. Turn engine off. Disconnect vacuum gauge from vacuum supply hose. Reinstall vacuum supply hose on EGR solenoid. Disconnect vacuum hose from top of EGR valve. Install vacuum gauge on disconnected vacuum hose.
  6. Start engine. Disconnect connector at EGR solenoid while observing vacuum gauge. If vacuum is more than 3 in. Hg, go to next step. If vacuum is 3 in. Hg or less, replace EGR valve assembly. Perform TEST VER-2A - ROAD TEST VERIFICATION .
  7. Turn engine off. Disconnect backpressure hose from signal tube at base of EGR valve. See Fig 1.
  8. Using shop air, apply 20 psi (1.4 kg/cm2 ) air pressure on signal tube at base of EGR valve. Open and close throttle while listening for a tone change. If tone does not change, go to next step. If tone changes, replace EGR valve assembly. Perform TEST VER-2A - ROAD TEST VERIFICATION .
  9. Remove shop air and reconnect backpressure hose on signal tube at base of EGR valve. Connect vacuum pump on vacuum hose fitting on top of EGR valve. Start engine.
  10. With engine idling, slowly apply vacuum to EGR valve while listening for a decrease in engine speed. If engine speed does not decrease, go to next step. If engine speed decreases, go to step  12.
  11. Remove EGR valve assembly. Inspect passages in EGR valve and intake manifold for restrictions. If all passages are open, replace EGR valve assembly. Perform TEST VER-2A - ROAD TEST VERIFICATION . If passages are restricted, clean passages as necessary and reinstall EGR valve. Perform TEST VER-2A - ROAD TEST VERIFICATION .
  12. Turn engine off. Apply 10 in. Hg of vacuum on EGR valve. Vacuum should hold for at least 30 seconds. If vacuum is maintained for 30 seconds, EGR system operation is normal. Test is complete. If vacuum cannot be maintained for 30 seconds, replace EGR valve assembly. Perform TEST VER-2A - ROAD TEST VERIFICATION .
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