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Test NTC-18A: Checking EGR System

NOTE: Perform TEST NTC-1A  or TEST NTC-17A  before proceeding.
  1. Disconnect vacuum supply hose at EGR solenoid. The EGR solenoid is located on top of EGR backpressure transducer.
  2. Install vacuum gauge on disconnected vacuum supply hose. Start engine. If vacuum is more than 10 in. Hg at idle, go to step 4)  . If vacuum is 10 in. Hg or less at idle, go to next step.
  3. Disconnect EGR solenoid vacuum supply hose at intake manifold. Install a vacuum gauge onto intake manifold nipple. 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 . If vacuum is 10 in. Hg or less at idle, repair plugged vacuum port on intake manifold. Perform TEST VER-2A .
  4. Disconnect vacuum gauge. Reconnect vacuum supply hose at EGR solenoid. Disconnect EGR valve hose from top of EGR valve. Connect a vacuum gauge to disconnected hose. While observing vacuum gauge, unplug EGR solenoid electrical connector. Raise engine speed slightly above idle and observe vacuum reading. If vacuum reading is more than 3 in. Hg, go to next step. If vacuum reading is 3 in. Hg or less, replace EGR valve assembly. Perform TEST VER-2A .
  5. Turn ignition off. Disconnect exhaust backpressure hose from bottom of EGR backpressure transducer. Adjust shop air supply to 20 psi (138 kPa). Using shop air supply adjusted to 20 psi (138 kPa), connect shop air to nipple on base of backpressure transducer. Backpressure transducer has EGR solenoid mounted on top of it. While opening and closing throttle, listen for a tone change. If tone changes, replace EGR valve assembly. Perform TEST VER-2A . If tone does not change, go to next step.
  6. Remove vacuum gauge. Cap open nipple at EGR backpressure transducer. Connect a hand vacuum pump to EGR valve nipple located on base EGR valve. Start engine. Apply vacuum to EGR valve. Listen for an engine speed change. If engine speed stayed the same, replace EGR valve assembly. Perform TEST VER-2A . If engine speed did not stay the same, go to next step.
  7. Turn ignition off. Apply 10 in. Hg of vacuum to nipple on base of EGR valve and hold for 30 seconds. If vacuum held for 30 seconds, EGR system is functioning normal. Test is complete. If vacuum did not hold for 30 seconds, replace EGR valve assembly. Perform TEST VER-2A .
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