1997 Lexus SC 300 AutomaticFACTORY OEM SERVICE PROCEDURE

ACIS Intake Air Control System

  1. Install a 3-way vacuum "T" fitting in vacuum hose between IACV actuator and ACIS Vacuum Switch Valve (VSV). See Figure. Connect a vacuum gauge to vacuum "T" fitting. Start engine. With engine idling, ensure no vacuum reading is obtained.
  2. Fully open throttle and ensure vacuum reading momentarily reads at least 10 in. Hg and IACV actuator rod pulls downward. If IACV actuator rod pulls downward, no problem is indicated. If actuator valve rod fails to pull downward, go to next step.
  3. Remove air intake chamber (if necessary) to access intake air control valve. See Figure. Apply about 15 in. Hg to IACV actuator. If IACV actuator rod does not move, replace IACV actuator.
  4. If IACV actuator rod moves, check to see if diaphragm holds vacuum for at least one minute. If diaphragm does not hold vacuum, replace actuator. If diaphragm holds vacuum, ensure IACV plate is fully closed. If IACV plate is not fully closed, turn adjusting screw as necessary. If no problem is indicated, check ACIS vacuum tank. See ACIS VACUUM TANK .
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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.

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