1987 Mitsubishi Starion ESI-RFACTORY OEM SERVICE PROCEDURE

Idle Speed Control & Throttle Position Sensor: Mirage

  1. Engine coolant temperature should be 185-205°F (85-95°C). Turn lights, cooling fan and accessories off. Place transmission in Neutral or Park. Place steering wheel in straight-ahead position. Loosen accelerator cable.
  2. Disconnect TPS connector. Connect Harness (MD998459 ) between separated connectors. Connect a voltmeter between terminals No. 2 (Blue: Output) and 1 (Black: Ground).
  3. Turn ignition on (do not start engine) and hold 15 seconds or more. This will set ISC motor at idle position. Turn ignition switch to "LOCK" position. Disconnect ISC servo motor connector. Put ISC motor in idle position.
  4. Open throttle valve by hand 2-3 times and allow to return with a snap each time. Loosen fixed servo adjusting screw. See Figure.
  5. Start engine and run at idle. Check engine speed and motor position sensor output voltage. Engine speed should be 700 RPM. Output voltage should be .9 volts. If not to specification, adjust using ISC adjusting screw. See Figure.
  6. Tighten fixed servo adjusting screw until RPM increases. Loosen screw until RPM ceases to drop, then loosen screw 1/2 turn.
  7. Stop engine. Turn ignition on (engine does not start) and check TPS output voltage. Voltage should be .48-.52 volts. If not to specification, loosen TPS screws and adjust by turning (clockwise increases voltage). Tighten screws after adjustment.
  8. Turn ignition off. Adjust accelerator cable. Connect ISC motor connector. Disconnect harness and voltmeter. Connect TPS connector.
  9. Start engine and check that idle speed is correct. Turn ignition off. Disconnect battery for 5-6 seconds to erase diagnosis memory. Reconnect battery.
Factory Service Tools

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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.