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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. 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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