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BACKPRESSURE Variable Transducer EGR System

  1. Check vacuum lines for correct routing. Disconnect Idle Speed Control (ISC) connector (EFI only). Disconnect and plug vacuum supply hose from EGR valve nipple. Start engine and ensure engine idle speed is within specification.
  2. Using hand-held vacuum pump, slowly apply 5-10 in. Hg to EGR valve. Engine speed should drop at least 100 RPM or stall. Vacuum should not drop more than 1 in. Hg in 30 seconds.
  3. Reconnect ISC connector and EGR supply hose. Disconnect vacuum connector at backpressure variable transducer. Gently blow into center port of transducer until relief valve closes.
  4. Apply 5-10 in. Hg to bottom port of transducer and hold. Transducer should hold vacuum at bottom port as long as pressure is applied to center port.
  5. Using a "T" fitting, apply 5-10 in. Hg to bottom and top ports of transducer. Transducer should hold vacuum. If system does not respond as indicated, test EGR control system. If testing is required, see appropriate COMPONENT TESTING article in the EMISSION section.
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