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High Altitude

  1. Warm up engine and check ignition timing at idle. Disconnect hose from distributor sub-diaphragm, and plug hose end.
  2. Check ignition timing. Timing should be 5° BTDC. Reconnect hose to sub-diaphragm. Verify that timing advances to about 12° BTDC.
    Fig 1: HAC System
    G38379Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002
  3. Disconnect vacuum hose between check valve and vacuum pipe at vacuum pipe side. Plug pipe end.
  4. Disconnect 3 hoses from top of HAC valve. Blow air into each hose and check that air flows into carburetor. Reconnect hoses to proper locations.