Mitsubishi Eclipse 1990-1998 Repair Guide

Exhaust Gas Recirculation System

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OPERATION



See Figure 1

The Exhaust Gas Recirculation (EGR) system is used to reduce Oxides of Nitrogen (NOx) in the engine exhaust. This is accomplished by allowing a predetermined amount of hot exhaust gas to recirculate and dilute the incoming air and fuel mixture. This process reduces peak flame temperature during combustion. The system uses a vacuum-controlled Exhaust Gas Recirculation (EGR) valve, in order to modulate exhaust gas flow from the exhaust manifold into the intake manifold.



Click image to see an enlarged view

Fig. Fig. 1: Typical EGR system schematic-2.4L engine shown, others similar

COMPONENT TESTING



EGR Valve

See Figure 2

  1. Remove the EGR valve from the vehicle. Check for sticking of plunger caused by excess carbon deposits. If such a condition exists, clean with appropriate solvent so the valve seats correctly.
  2.  
  3. Connect a vacuum pump to the valve and apply 20 in. Hg (67 kPa) of vacuum.
  4.  
  5. Check for air tightness. If the valve has 2 vacuum ports; pick one and plug the other. The vacuum must be retained.
  6.  
  7. For 1990-94 vehicles, blow air from 1 passage of the EGR to check condition as follows:
    1. With 1.8 in. Hg (6 kPa) of vacuum or less applied to the valve, air should not pass through the valve.
    2.  
    3. With 8.5 in. Hg (28.7 kPa) of vacuum or more applied to the valve, air should pass through the valve.
    4.  

  8.  



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Fig. Fig. 2: Use a vacuum pump to test the EGR

  1. For 1995-98 vehicles, apply vacuum (specified below) and check the passage of air by blowing through either side of the EGR passages, as follows:
    1. With 1.6 in. Hg or less of vacuum applied to the valve, air should blow out of the opposite passage.
    2.  
    3. With 8.7 in. Hg or more of vacuum applies to the valve, air should not blow out of the opposite passage.
    4.  

  2.  
  3. If the results are not as described, replace the EGR valve.
  4.  

System Operation
1990-94 FEDERAL AND CANADIAN VEHICLES
  1. Disconnect the green striped vacuum hose from the throttle body, then connect a hand-held vacuum pump to the vacuum hose.
  2.  
  3. Plug the nipple from which the vacuum hose was disconnected.
  4.  
  5. Under the engine conditions listed below, inspect the system operation by applying vacuum from a hand held vacuum pump.
  6.  
  7. With the engine temperature cold, 104°F (40°C) or below, the response should be as follows:
    1. Engine at idle-vacuum should leak
    2.  

  8.  
  9. With the engine at temperature of 176°F (80°C) or higher, the response should be as follows:
    1. With 1.8 in. Hg (6 kPa) of vacuum applied-the engine should idle and vacuum should be maintained.
    2.  
    3. With 8.5 in. Hg (29 kPa) of vacuum applied-the engine should change from idling to slightly unstable and the vacuum should be maintained.
    4.  

  10.  
  11. If the test results differ from those listed, thoroughly inspect the EGR system components.
  12.  

1990-94 CALIFORNIA VEHICLES

See Figure 3

  1. Disconnect the green striped vacuum hose from the EGR valve and connect a hand vacuum pump through a 3-way connector. The pump will now be installed in the line.
  2.  
  3. With engine cold (below 68°F), test system operation as follows:
    1. Race the engine by rapidly operating the accelerator.
    2.  
    3. Measure the pressure reading on the pump. The negative pressure at the valve should not change.
    4.  

  4.  
  5. With the engine warm (68°F or more), test system operation as follows:
    1. Race the engine by rapidly operating the accelerator.
    2.  
    3. The negative pressure at the gauge rises to 3.9 in. Hg (13 kPa) or more.
    4.  

  6.  
  7. Disconnect the 3-way terminal and connect a hand vacuum pump to the EGR valve.
  8.  



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Fig. Fig. 3: Apply vacuum to the EGR valve to inspect system operation

  1. When a negative pressure of 8.5 in. Hg (29 kPa) is applied during engine idling, check that the engine stops or the idle becomes unstable.
  2.  
  3. Inspect the system components if test results differ from specifications listed above.
  4.  

1995-98 2.0L NON-TURBO ENGINES
  1. Check the EGR control system and the valve with the engine fully warmed up running. The engine coolant temperature should be over 170°F (76°C.)
  2.  
  3. With the transaxle in Neutral, and the throttle close, let the engine idle for about 70 seconds.
  4.  
  5. Quickly accelerate the engine to about 2,000 rpm, but do not go over 3000 rpm.
  6.  
  7. The EGR valve stem should move when accelerating the engine. Repeat the test several times to confirm movement.
  8.  
  9. If the EGR valve stem moves, the control system is operating normally.
  10.  
  11. Disconnect and plug the vacuum hose from the EGR valve.
  12.  
  13. Connect a vacuum pump to the EGR valve. Check to see if the engine stalls or if the idle is unstable when a vacuum of 3.5 in. Hg (12 kPa) or higher is applied while the engine is idling.
  14.  

1995-98 2.0L TURBO AND 2.4L ENGINES

See Figures 4 and 5

  1. Disconnect the vacuum hose (the 2.0L turbo has a green stripe and the 2.4L engine has a white stripe), then connect a hand-held vacuum pump to the 3-way terminal.
  2.  
  3. Check the condition of the vacuum when the engine has been raced rapidly, as follows:
    1. When the engine is cold, coolant temperature at 68°F (20°C) or less, and the throttle is opened quickly, no vacuum should generate (it should remain as barometric pressure).
    2.  
    3. When the engine is hot, coolant temperature at 176°F (80°C) or higher, and the throttle quickly opened, the vacuum should momentarily rise over 3.9 in. Hg (13 kPa).
    4.  

  4.  



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Fig. Fig. 4: Location of the EGR solenoid and vacuum hose-2.0L turbo engine



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Fig. Fig. 5: EGR solenoid and vacuum line location-2.4L engine

  1. Disconnect the 3-way terminal.
  2.  
  3. Connect the vacuum pump right to the EGR valve.
  4.  
  5. Check to see if the engine stalls or if the idle is unstable when a vacuum of 7.9 in. Hg or higher is applied while the engine is idling.
  6.  

EGR Temperature Sensor

See Figure 6

The EGR temperature sensor is used on California vehicles only. The EGR temperature sensor detects the temperature of the gas passing through the EGR control valve. It converts the detected temperature into an electrical voltage signal which is sent the vehicles Engine Control Unit (ECU). If the circuit of the EGR temperature sensor is broken, the warning light will come on.

  1. Remove the EGR temperature sensor from the engine.
  2.  



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Fig. Fig. 6: Put the EGR temperature sensor in a container of water, then measure resistance as the water temperature is increased

  1. Place the EGR sensor into water. While increasing the temperature of the water, measure the sensor resistance. Compare the values to following specifications:
    1. 122°F (50°C)-60-83 k.ohms resistance
    2.  
    3. 212°F (100°C)-11-14 k.ohms resistance
    4.  

  2.  
  3. If the resistance obtained varies significantly from specifications, replace the sensor.
  4.  

Thermal Vacuum Valve
1992-94 FEDERAL AND CANADIAN 2.0L ENGINES

See Figure 7

  1. Label and disconnect the vacuum hose at the thermo valve.
  2.  
  3. Connect a hand held vacuum pump to the vacuum hose on the thermo valve.
  4.  



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Fig. Fig. 7: Testing the thermal vacuum valve-2.0L engine (Federal) shown, others similar

  1. Apply vacuum and check the air passage through the thermo valve. Compare results to the following specifications:
    1. Engine coolant temperature of 122°F (50°C) or less-vacuum leaks
    2.  
    3. Engine coolant temperature of 176°F (80°C) or more-vacuum is maintained
    4.  

  2.  
  3. If the results differ from the desired specifications, replace the valve.
  4.  

EGR Port Vacuum Check

See Figures 8 and 9

  1. Disconnect the vacuum hose from the throttle body EGR vacuum nipple. Connect a hand-held vacuum pump to the nipple.
  2.  



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Fig. Fig. 8: Connect a vacuum pump to the EGR vacuum nipple on the throttle body-1995-98 2.0L non-turbo engine shown



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Fig. Fig. 9: Location of the throttle body EGR valve vacuum nipple-2.4L engine shown

  1. Start the engine, then slowly raise the speed and compare with the following specifications.
    1. For 1990-94 vehicles, check to be sure the vacuum raised proportionally with the rise in engine speed.
    2.  
    3. For 1995-98 vehicles, the vacuum reading on the pump should remain constant.
    4.  

  2.  

EGR Solenoid
1990-94 VEHICLES

See Figures 10 and 11

  1. Label and disconnect the yellow and green striped vacuum hose from the EGR solenoid.
  2.  
  3. Disconnect the electrical harness connector.
  4.  
  5. Connect a hand vacuum pump to the nipple to which the green-striped vacuum hose was connected.
  6.  
  7. Apply a vacuum and check for air-tightness when voltage is applied and discontinued. When voltage is applied, the vacuum should be maintained. When voltage is discontinued, vacuum should leak.
  8.  



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Fig. Fig. 10: Apply voltage to the EGR solenoid using jumper wires and check for air-tightness using a vacuum pump



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Fig. Fig. 11: Measure the resistance between the terminals of the EGR solenoid

  1. Measure the resistance between the terminals of the solenoid valve. The resistance should be 36-44 ohms at 68°F (20°C).
  2.  
  3. If the test results differ from the specifications, replace the EGR solenoid.
  4.  

1995-98 2.0L NON-TURBO ENGINE

See Figure 12

On these engines, the solenoid is referred to as an electric EGR transducer solenoid.

  1. Disconnect the vacuum hose from the electric EGR transducer.
  2.  
  3. Detach the harness connector.
  4.  
  5. Plug nipple A, then connect a hand vacuum pump to nipple B.
  6.  
  7. Use a jumper wire to connect the solenoid terminal to the battery terminal.
  8.  
  9. Turn on and off the negative battery terminal side under wire and apply vacuum and positive pressure to check the air tightness. Compare with the following specifications:
  10.  



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Fig. Fig. 12: Electric EGR transducer solenoid test connections-1995-98 2.0L non-turbo engine

    1. With the jumper wire disconnected and pressure not applied, vacuum should leak.
    2.  
    3. With the jumper wire disconnected and pressure applied, the vacuum should be maintained.
    4.  
    5. With the jumper wire connected and pressure not applied, vacuum should be maintained.
    6.  


  1. Measure the resistance between the terminals of the solenoid. The resistance should be 25-35 ohms at 68°F (20°C).
  2.  
  3. If the test results differ from the specifications, replace the solenoid.
  4.  

1995-98 2.0L TURBO AND 2.4L ENGINES

See Figures 13 and 14

Before disconnecting the vacuum hoses, tag them to assure proper connection during installation

  1. Tag and disconnect the vacuum hose (2.0L turbo engine: yellow stripe, white and green stripe, 2.4L engine: yellow stripe and white stripe) from the solenoid valve.
  2.  
  3. Detach the harness connector.
  4.  
  5. Connect a hand-held vacuum pump to the nipple to which the white stripe vacuum hose was connected (2.0L turbo) or the A nipple (2.4L).
  6.  
  7. Check air tightness by applying a vacuum with voltage applied directly from the battery to the EGR control solenoid valve and without applying voltage.
  8.  



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Fig. Fig. 13: Checking the EGR solenoid-2.0L turbo engine



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Fig. Fig. 14: EGR solenoid check connections-2.4L engine

  1. For 2.0L turbo engines, compare with the following:
    1. With battery voltage not applied and the B nipple open, vacuum should be maintained.
    2.  
    3. With battery voltage applied and the B nipple open, vacuum should leak.
    4.  
    5. With battery voltage applied and the B nipple closed, vacuum should be maintained.
    6.  
    7. For the 2.4L engines, compare with the following:
    8.  
    9. With battery voltage not applied, vacuum should be maintained.
    10.  
    11. With battery voltage applied, vacuum should leak.
    12.  

  2.  
  3. Using an ohmmeter, measure the resistance between the solenoid valve terminals. The resistance should fall between 36-44 ohms when the engine temperature is 68°F (20°C).
  4.  

REMOVAL & INSTALLATION



EGR Valve

See Figure 15

  1. Disconnect the negative battery cable.
  2.  
  3. Remove the air cleaner and intake hoses as required.
  4.  
  5. Tag and disconnect the vacuum hose from the EGR valve.
  6.  
  7. Remove the mounting bolts and the EGR valve from the engine.
  8.  
  9. Clean the mating surfaces on the valve and the engine. Make sure to remove all gasket material.
  10.  
  11. Inspect the valve for a sticking plunger, caused by excess carbon deposits. If such a condition exists, clean with appropriate solvent so valve seats correctly.
  12.  



Click image to see an enlarged view

Fig. Fig. 15: EGR valve location-late model 2.0L turbo engine shown, others similar

To install:
  1. Install EGR valve with a new gasket in place.
  2.  
  3. Install the mounting bolts and tighten as follows:

    1.8L engine-7-10 ft. lbs. (10-15 Nm).
     
    1990-94 2.0L engine-10-15 ft. lbs. (15-22 Nm).
     
    1995-98 engines-16 ft. lbs. (22 Nm).
     

  4.  
  5. Connect the vacuum hose to the EGR valve.
  6.  
  7. Install the air cleaner and air intake hoses as required.
  8.  
  9. Connect the negative battery cable.
  10.  

EGR Temperature Sensor
  1. Disconnect the negative battery cable.
  2.  
  3. Detach the electrical connector from the sensor.
  4.  
  5. Remove the sensor from the engine.
  6.  

To install:
  1. Install the sensor to the engine and tighten to 8 ft. lbs. (12 Nm).
  2.  
  3. Attach the electrical connector to the sensor.
  4.  
  5. Connect the negative battery cable.
  6.  

Thermal Vacuum Valve
  1. Disconnect the negative battery cable.
  2.  
  3. Detach the vacuum line from the thermo valve.
  4.  
  5. Using a wrench, remove the valve from the engine.
  6.  

When removing or installing the valve, do not allow wrenches or other tool to contact the resin part of the valve. Damage to the valve may occur.

  1. Inspect the vacuum hose for cracks and replace as required.
  2.  

To install:
  1. Apply sealant to the threads of the thermo valve and install into the engine.
  2.  
  3. Tighten the valve to 15-30 ft. lbs. (20-40 Nm). When installing the valve, do not allow the wrench to come in contact with the resin part of the valve.
  4.  
  5. Attach the vacuum hose to the valve.
  6.  
  7. Connect the negative battery cable.
  8.  

EGR Solenoid

See Figures 16 and 17

  1. Disconnect the negative battery cable.
  2.  
  3. Label and disconnect the vacuum hoses from the EGR solenoid.
  4.  
  5. Disconnect the electrical harness from the solenoid.
  6.  
  7. Remove the solenoid from the mounting bracket and replace as required.
  8.  



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Fig. Fig. 16: Location of the electric EGR transducer solenoid-1995-98 2.0L non-turbo engine



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Fig. Fig. 17: On most vehicles, the EGR solenoid is mounted to the firewall

To install:
  1. Install the solenoid to the mounting bracket and secure in position.
  2.  
  3. Attach the electrical connector.
  4.  
  5. Connect the vacuum hoses to the solenoid making sure they are installed in their original location.
  6.  
  7. Connect the negative battery cable.
  8.  

Thermal Vacuum Valve
  1. Disconnect the negative battery cable.
  2.  
  3. Disconnect the vacuum line from the thermo valve.
  4.  
  5. Using a wrench, remove the valve from the engine.
  6.  

When removing or installing the valve, do not allow wrenches or other tool to contact the resin part of the valve. Damage to the valve may occur.

  1. Inspect the vacuum hose for cracks and replace as required.
  2.  

To install:
  1. Apply sealant to the threads of the thermo valve and install into the engine.
  2.  
  3. Tighten the valve to 15-30 ft. lbs. (20-40 Nm). When installing the valve, do not allow the wrench to come in contact with the resin part of the valve.
  4.  
  5. Reconnect the vacuum hose to the valve.
  6.  
  7. Reconnect the negative battery cable.
  8.  

Manifold Differential Pressure Sensor

See Figure 18

  1. Disconnect the negative battery cable.
  2.  
  3. Unfasten the sensor electrical connector.
  4.  



Click image to see an enlarged view

Fig. Fig. 18: Manifold differential pressure sensor location-1995-98 2.0L turbo engine

  1. Unfasten the retaining bolts, then remove the sensor from the vehicle.
  2.  
  3. Installation is the reverse of the removal procedure.
  4.  

 
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