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Vacuum Modulator

  1. Check vacuum modulator filters for contamination or damage. Using compressed air, clean filters. Disconnect vacuum hoses from ports P, Q and R of vacuum modulator. Plug ports P and R, and blow air into port Q. Air should escape through air filter of modulator.
  2. Start engine and maintain engine speed at 3000 RPM on Pickup. Blow through port Q again. There should be strong resistance to air flow. If not, replace vacuum modulator. Reconnect vacuum hoses to proper locations.
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