Mitsubishi Eclipse 1990-1998 Repair Guide

Intake Air Temperature (IAT) Sensor

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OPERATION



See Figures 1 and 2

The intake air temperature sensor (provided on the air flow sensor on all engines, except the 1995-98 2.0L non-turbo) is a resistor which measures the intake air temperature. The ECU will determine the intake air temperature according to the output voltage from the sensor, and compensates the fuel injection amount according to the intake air temperature.



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Fig. Fig. 1: Location of the intake air temperature sensor (integral with the volume air flow sensor)-1990-94 vehicles



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Fig. Fig. 2: On 1995-98 2.0L non-turbo engines, the IAT sensor is mounted on the intake plenum

When the intake air temperature sensor is faulty, it controls the fuel injection amount based on an intake air temperature default of 77°F (25°C). The driveability of the vehicle may become poor during cold temperature operation. The trouble may not be noticeable when the ambient temperature is around 77°F (25°C).

TESTING



Except 1995-98 2.0L Non-Turbo Engine

See Figures 3, 4 and 5

  1. Detach the air flow sensor electrical connector.
  2.  



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Fig. Fig. 3: IAT sensor terminal identification-1990-94 vehicles



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Fig. Fig. 4: IAT sensor terminal identification-1995-98 2.0L turbo and 2.4L engines



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Fig. Fig. 5: Measure the intake air temperature sensor resistance while heating it with a hair drier

  1. If equipped with non-turbo engines, measure the resistance between terminals No. 4 and No. 6 of the electrical connector.
  2.  
  3. If equipped with turbo engine, measure the resistance between terminals No. 6 and No. 8 of the sensor electric connector.
  4.  
  5. Compare test readings to specifications:
    1. Sensor temperature of 32°F (0°C)-5.3-6.7 kilo-ohms
    2.  
    3. Sensor temperature of 68°F (20°C)-2.3-3.0 kilo-ohms
    4.  
    5. Sensor temperature of 176°F (80°C)-0.30-0.42 kilo-ohms
    6.  

  6.  
  7. Measure the sensor resistance while heating the sensor area with a hair dryer. As the temperature of the sensor increases, sensor resistance should become smaller.
  8.  
  9. If the measured resistance deviates from the standard value or the resistance remains unchanged, replace the air flow sensor assembly.
  10.  

1995-98 2.0L Non-Turbo Engine

See Figure 6

  1. Detach the IAT sensor connector.
  2.  
  3. If necessary, you can remove the sensor to test it.
  4.  
  5. Use a DVOM to measure the resistance between the sensor terminals and compare with the following specifications:
    1. At 77°F (25°C), the resistance should be 9-11 kilo-ohms.
    2.  
    3. At 212°F (100°C), the resistance should be 0.6-0.8 ohms.
    4.  

  6.  



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Fig. Fig. 6: Use an ohmmeter (1) to measure the resistance of the IAT sensor (2). Note that this sensor is within specifications

  1. If the resistance is not within the specified range, replace the sensor.
  2.  
  3. If removed, install the sensor. Attach the connector.
  4.  

REMOVAL & INSTALLATION



Except 1995-98 2.0L Non-Turbo Engines

See Figure 1

  1. Disconnect the negative battery cable.
  2.  
  3. Unplug the sensor electrical connector from the sensor.
  4.  
  5. If necessary, carefully remove the lid of the air filter housing.
  6.  
  7. Unfasten the retainers, then remove the sensor from the air cleaner housing.
  8.  
  9. Installation is the reverse of the removal procedure.
  10.  

1995-98 2.0L Non-Turbo Engines

See Figures 7, 8 and 9

  1. Disconnect the negative battery cable.
  2.  
  3. Detach the IAT sensor harness connector.
  4.  



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Fig. Fig. 7: Unplug the IAT sensor electrical connector

  1. Unthread the IAT sensor and remove from the intake plenum.
  2.  



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Fig. Fig. 8: Use a open-end wrench to loosen ...



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Fig. Fig. 9: ...then remove the IAT sensor from the vehicle

To install:
  1. Apply Loctite® 24200 or equivalent sealant to the threads of the sensor and install in the intake plenum. Tighten the sensor to 5 ft. lbs. (7 Nm.
  2.  
  3. Attach the sensor electrical connector. Make sure it is connected securely.
  4.  
  5. Connect the negative battery cable.
  6.  

 
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