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Test NTC-18A: Checking EGR System

NOTE: Perform TEST NTC-1A: NO TROUBLE CODES (NTC) TESTS  before proceeding.
  1. Disconnect vacuum supply hose to EGR solenoid. Connect a vacuum gauge to disconnected vacuum supply hose. Start engine. Observe vacuum gauge. If vacuum is more than 10 in. Hg at idle, go to step  3. If vacuum is 10 in. Hg or less, go to next step.
  2. Disconnect EGR vacuum supply hose at intake manifold. Connect a vacuum gauge to intake manifold nipple. Observe vacuum gauge with engine idling. If vacuum is more than 10 in. Hg, repair restriction or leak in vacuum hose to EGR solenoid. Perform TEST VER-2A: ROAD TEST VERIFICATION . If vacuum is 10 in. Hg or less, repair plugged vacuum nipple. Perform TEST VER-2A: ROAD TEST VERIFICATION .
  3. Disconnect vacuum gauge. Reconnect vacuum hose to EGR solenoid. Disconnect EGR valve hose from EGR valve. Connect vacuum gauge to disconnected EGR valve hose. While observing vacuum gauge, disconnect EGR solenoid electrical connector. Raise engine speed slightly more than idle and observe 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 .
  4. Turn ignition off. Disconnect exhaust back pressure hose. Adjust shop air to 20 psi. Connect shop air to nipple on base of transducer. While opening and closing throttle, listen for a tone change. If tone changes, replace EGR valve assembly. Perform TEST VER-2A: ROAD TEST VERIFICATION . If tone does not change, go to next step.
  5. Remove vacuum gauge. Cap open nipple at transducer. Connect a hand vacuum pump to EGR valve nipple. Start engine. While applying vacuum to EGR valve, listen for an engine speed change. If engine speed stayed the same, replace EGR valve assembly. Perform TEST VER-2A: ROAD TEST VERIFICATION . If engine speed did not stay the same, go to next step.
  6. Turn ignition off. Apply 10 in. Hg of vacuum and hold for 30 seconds. If vacuum held for 30 seconds, EGR system is normal. Test is complete. If vacuum did not hold for 30 seconds, replace EGR valve assembly. Perform TEST VER-2A: ROAD TEST VERIFICATION .
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