1994 Mitsubishi Eclipse Base, AutomaticFACTORY OEM SERVICE PROCEDURE

Eclipse 2.0L

  1. Using a stethoscope, listen for operating sound of IAC motor when ignition switch is placed in ON position. If no operating sound can be heard, proceed with following tests.
  2. Disconnect IAC harness connector. Install Test Harness (MD998463-01 ) if necessary to aid testing. Using DVOM, measure resistance between IAC terminals No. 1 and 2 and between terminals No. 1 and 3. See Fig 1 . Resistance should be 28-33 ohms.
  3. Measure resistance between terminals No. 4 and 5 and between terminals No. 5 and 6. Resistance should be 28-33 ohms. If resistance measurements are not within specification, replace IAC motor. Go to step 4) if IAC motor is within specification.
  4. Remove throttle body. See REMOVE/INSTALL/OVERHAUL article. Remove stepper motor from throttle body. Connect Test Harness (MD998463-01) to IAC motor.
  5. Hold IAC motor in hand. Place thumb on top of plunger. Connect positive lead of 6-volt power source to White and Green clips of test harness. Individually connect, then disconnect, negative lead of power source to Red and Black clips, Blue and Black clips, Blue and Yellow clips, and Red and Yellow clips. Finish by connecting negative lead to Red and Black clips again.
  6. Connect negative lead to test leads in reverse sequence of step 5). Stepper motor should vibrate with each connection. Replace IAC motor if vibration is not felt with each connection.
  7. Ensure MFI relay is functioning properly. See RELAYS  under MOTORS, RELAYS & SOLENOIDS. Disconnect IAC motor harness connector. Turn ignition on. Using DVOM, check for battery voltage between terminal No. 2 and vehicle ground and terminal No. 5 and vehicle ground. If voltage is not battery voltage, check and repair circuits between MFI relay and IAC motor. If battery voltage exists, go to step 8).
  8. This step checks for continuity between MFI relay and IAC motor. Check for continuity between MFI relay terminals No. 4 and 5 and IAC motor terminals No. 2 and 5. See Figure and Fig 1 . If continuity exists, go to step 9). If continuity does not exist, check and repair circuits.
  9. This step checks for continuity between ECM and IAC motor. Disconnect ECM harness connector. Check continuity of specified circuits. See Figure and Fig 1 . See IAC TO ECM CIRCUIT CONTINUITY CHECK  table. Check and repair any circuits without continuity.
    IAC TO ECM CIRCUIT CONTINUITY CHECK

    IAC Terminal No. ECM Terminal No.
    Eclipse 2.0L
    1 58
    3 59
    4 67
    6 68
  10. Connect ECM harness connector. Install harness connector and Test Harness (MB998463-01 ). Using engine analyzer with oscilloscope capability, connect special patterns probe to selected leads of test harness. Leads used are Red, Green, Black and Yellow clips.
  11. Start engine, and allow it to idle. Connect special patterns probe to one test lead. Turn A/C on. When IAC motor operates to increase engine speed to compensate for A/C system, a waveform should be displayed. Conduct test with each remaining test lead and compare pattern to illustration. See Fig 2 .
  12. If waveform is different, replace IAC motor. If all preceding tests do not show any system or component malfunction and ECM is suspected, replace ECM and retest system.
    Fig 1: Identifying IAC Motor Connectors (Eclipse 2.0L)
    G93G78473Courtesy of MITSUBISHI MOTOR SALES OF AMERICA.
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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.