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Home >> Toyota >> 1990 >> Celica All-Trac >> Repair and Diagnosis >> Engine Performance >> System >> Engine Controls - System/Component Tests >> Idle Control Systems >> Idle-Up System >> (3S-GE Engine)
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(3S-GE Engine)

  1. Engine should be at normal operating temperature with all accessories off. Connect tachometer to engine. See ADJUSTMENTS for tachometer attachment points. Start engine.
  2. Disconnect idle-up vacuum switching valve connector. Idle-Up System Vacuum Switching Valve is Located at the rear of the cylinder head. Turn in idle speed adjusting screw (under rubber plug on throttle body) until RPM drops 500 RPM.
  3. Plug in vacuum switching valve connector. Engine speed should rise about 100 RPM. If engine RPM does not rise, reset idle speed.
  4. With engine idling, check for battery voltage at Orange wire of vacuum switching valve when headlights or rear defogger switch is turned on. If no, voltage is present check taillight relay, headlight switch, rear defogger switch and relay. Also check wiring.
  5. If voltage is okay, check idle-up vacuum switching valve. With engine off, unplug vacuum switching valve. There should be 33-39 ohms as measured across both vacuum switching valve terminals. There should be no continuity between either terminal and body of valve.
  6. Remove ohmmeter probes. Connect 12 volts to Orange wire terminal on valve and ground other terminal. Air should flow from one pipe of valve to other. Valve should NOT permit air flow when 12 volt source is removed.
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