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Idle Speed Stabilization System

  1. Engine oil temperature must be at 176°F (80°C) minimum. Ignition timing must be correct and A/C must be off. Connect Dwell Meter (VW 1367) using Adapter Cable (US 1112). Set "%" button on dwell meter and check duty cycle.
  2. Reading should be 26-30% with oxygen sensor connected. If not, adjust duty cycle. See TUNE-UP article in the TUNE-UP section.
  3. If reading shows 33% or 40%, make sure A/C is switched off. If A/C is off, check idle throttle switch function. Check for open circuit between idle switch and ECU connector.
  4. If reading is fluctuating between 20-25%, check for open circuit in RPM signal from ignition ECU. If reading is steady 25%, idle speed is incorrect. Check for air leaks in throttle body. If no leaks are found, check for open circuit between ECU and idle stabilizer control valve. If circuit is correct, replace control valve.
  5. Turn A/C on. Idle speed should increase by 100 RPM. If not, check for open circuit between A/C switch on dash and terminals No. 6 and 16 on ECU connector. Check for RPM increase of 100 RPM when A/C compressor cycles off.
  6. If idle speed goes over 1000 RPM when A/C compressor switches off, check compressor signal wire to ECU. Wire should go to ECU connector terminal No. 19 but has been interchanged with terminal No. 16. Check wiring diagram and correct.
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