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Exhaust Gas RECIRCULATION: Testing

  1. To determine whether EGR system is causing driveability or emissions problems, disconnect vacuum line at EGR valve. If problems stop, EGR system is at fault. If problems still exist, EGR valve may be stuck open, otherwise EGR system is not the cause.
  2. Disconnect EGR valve hose at thermal vacuum valve. Apply 4 in. Hg vacuum to hose, then remove vacuum suddenly. Valve should be heard to close. If not, remove and clean valve. If valve closes, then start engine and apply vacuum to valve with engine idling. Engine should run rough or stall. If not, replace valve.
  3. Disconnect hoses from EGR valve and throttle housing vacuum port(s). Blow through hoses. Air should not pass when engine is cold, but should pass with engine warm.
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