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Positive BACKPRESSURE EGR Valve

  1. Disconnect electrical connector from EGR solenoid. Place transmission in Neutral (man. trans.) or "P" (auto. trans.). Set parking brake and block drive wheels. Connect tachometer to engine.
  2. Ensure that fast idle speed is set to specified RPM. With engine at normal operating temperature, place fast idle screw on highest step of fast idle cam.
  3. Disconnect and plug vacuum hose at EGR valve. As vacuum hose is removed, watch for downward movement of diaphragm. This should be accompanied by an increase in engine speed.
  4. Reconnect vacuum hose. Diaphragm should move upward and engine speed should decrease.
  5. If engine speed change and diaphragm movement are noticed with vacuum hose removed or installed, EGR valve is operating properly. Reconnect electrical connector to EGR solenoid.
  6. If engine speed and diaphragm movement did not occur, remove EGR valve from engine. Connect a vacuum pump to EGR valve and apply a constant vacuum of 10 in. Hg. EGR valve should not open. If EGR valve does open, replace it.
  7. With vacuum still applied to EGR valve, direct a 15 psi air pressure stream directly into valve seat. EGR valve should open fully. If not, EGR valve should be cleaned.
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