High & Low Altitude

1985 Toyota Tercel DX, 4D Wagon, FWD, AutomaticSECTION High & Low Altitude
  1. Ensure engine is at normal operating temperature. Check ignition timing at idle. Disconnect hose from distributor sub-diaphragm, and plug hose end. Recheck ignition timing. Timing should be 5° BTDC. Reconnect hose to sub-diaphragm. Verify that timing advances to about 13° BTDC.
  2. Disconnect vacuum hose from check valve at Black side and plug hose end. Check that ignition timing remains stationary for more than 1 minute. If timing changes, replace check valve. Stop engine and reconnect hoses to proper location.
    Fig 1: HAC System
    G38380Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002
  3. Disconnect 2 hoses on top of HAC valve. Blow air into each hose and check that air flows into carburetor. Reconnect hoses to proper locations.
RENDER: 1.0x

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When to See a Mechanic

Stop DIY work and contact a certified mechanic immediately if any of the following apply:

  • You smell fuel, burning insulation, or see smoke.
  • Brakes feel soft, pull hard to one side, or make grinding noises.
  • The engine overheats, stalls repeatedly, or misfires under load.
  • You are missing required tools, torque specs, or safe lifting equipment.
  • You are not confident in the next step or safety outcome.