Toyota Camry 1983-1996 Repair Guide

Idle Air Control (IAC) Valve

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OPERATION



The ECM is programmed with specific engine speed values to respond to different engine conditions (coolant temperature, air conditioner on/off, etc.). Sensors transmit signals to the ECM which controls the flow of air through the bypass of the throttle valve and adjusts the idle speed to the specified value. Some vehicles use an Idle Speed Control (ISC) valve while others use an Air Valve (AV) or Idle Air Control (IAC) valve to control throttle body by-pass air flow.

TESTING



2S-ELC Engine
  1. With the engine running and the coolant temperature below 140°F (60°C), pinch off the Air Valve hose and verify that the idle is reduced by no more than a 100 rpm.
  2.  
  3. Unplug the valve wire connector and measure the coil resistance with an ohmmeter. It should be 40-60 ohms with the coolant temperature at 176°F (80°C) and the air valve closed.
  4.  
  5. If not as specified, replace the valve.
  6.  

3S-FE and 5S-FE Engines

See Figures 1, 2 and 3

The idle speed must be set correctly before testing the ISC valve.

  1. Bring the engine to normal operating temperature with transmission in N.
  2.  
  3. Using a jumper wire, connect the terminals TE1 and El of the check connector (DLC 1).
  4.  



Click image to see an enlarged view

Fig. Fig. 1: Attach a jumper wire to the terminals TE1 and E1 in the DLC 1

  1. The engine rpm should rise to 900-1300 rpms for 5 seconds. Check that it returns to idle speed. If rpm is as specified, the valve is functioning properly.
  2.  
  3. If rpm did not function as specified, stop the engine and disconnect the jumper wire.
  4.  
  5. Disengauge the ISC valve connector.
  6.  
  7. Using an ohmmeter, measure the resistance between the +B terminal (middle terminal) and the ISC1-ISC2 (3S-FE) and the ISCC-ISCO (5S-FE) outer terminals.
  8.  



Click image to see an enlarged view

Fig. Fig. 2: Attach an ohmmeter and measure the resistance between the three terminals-3S-FE engine



Click image to see an enlarged view

Fig. Fig. 3: Attach an ohmmeter and measure the resistance between the three terminals-5S-FE engine

  1. The resistance should be 16-17 ohms on the 3S-FE engine and 19.3-22.3 ohms on the 5S-FE engine.
  2.  
  3. If not as specified, replace the ISC valve.
  4.  

1MZ-FE Engine

See Figures 4 and 5

The idle speed must be set correctly before testing the valve. Make sure the A/C is off during testing.



Click image to see an enlarged view

Fig. Fig. 4: The IAC valve is attached to the lower portion of the throttle body

  1. Bring the engine to normal operating temperature with transmission in N.
  2.  
  3. Using a jumper wire, connect the terminals TE1 and El of the check connector (DLC 1).
  4.  
  5. The engine rpm should rise to 1000 rpms for 5 seconds. Check that it returns to idle speed. If rpm is as specified, the valve is functioning properly.
  6.  
  7. If rpm did not function as specified, stop the engine and disconnect the jumper wire.
  8.  
  9. Disengage the ISC valve connector.
  10.  
  11. Using an ohmmeter, measure the resistance between the +B terminal (middle terminal) and the RSC and RSO outer terminals.
  12.  



Click image to see an enlarged view

Fig. Fig. 5: Attach an ohmmeter and measure the resistance between the three terminals-1MZ-FE engine

  1. The resistance should be 21-28.5 ohms on a hot engine.
  2.  
  3. If not as specified, replace the ISC valve.
  4.  

2VZ-FE and 3VZ-FE Engines

See Figures 6, 7 and 8

  1. Disengage the ISC valve connector.
  2.  
  3. Using an ohmmeter, measure the resistance between the B1 terminal (lower middle terminal) and the S1 or S3 (lower outer terminals), and between B2 terminal (upper middle terminal) and the S2 or S4 (upper outer terminals).
  4.  



Click image to see an enlarged view

Fig. Fig. 6: ISC terminal identification-2VZ-FE and 3VZ-FE engines

  1. If the resistance is not 10-30 ohms, replace the ISC valve.
  2.  
  3. Apply battery voltage to terminals B1 and B2 while repeatedly grounding S1, S2, S3, S4, S1 in sequence. Check that valve moves toward the closed position.
  4.  



Click image to see an enlarged view

Fig. Fig. 7: Testing the IAC using battery voltage to see if the valve will close-2VZ-FE and 3VZ-FE engines

  1. Apply battery voltage to terminals B1 and B2 while repeatedly Grounding S4, S3, S2, S1, S4 in sequence. Check that valve moves toward the opened position.
  2.  



Click image to see an enlarged view

Fig. Fig. 8: Testing the IAC using battery voltage to open the valve-2VZ-FE and 3VZ-FE engines

  1. If valve does not function as specified, replace the ISC valve.
  2.  

REMOVAL & INSTALLATION



2S-ELC Engine
  1. Disconnect the air valve wiring.
  2.  
  3. Disconnect the air hoses attached to the valve.
  4.  
  5. Remove the two bolts and extract the valve from the cylinder head rear cover.
  6.  

To install:
  1. Install the air valve with the two bolts.
  2.  
  3. Attach the air hoses and secure the clamps.
  4.  
  5. Attach the wiring to the valve.
  6.  

1MZ-FE, 3S-FE and 5S-FE Engines

See Figures 9, 10 and 11



Click image to see an enlarged view

Fig. Fig. 9: Exploded view of the Idle Speed Control (ISC) valve

  1. Remove the throttle body from the vehicle.
  2.  
  3. Remove the four screws that attach the idle speed control (ISC) valve to the throttle body.
  4.  
  5. Lift the ISC valve from the throttle body and remove the gasket.
  6.  



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Fig. Fig. 10: The idle air control valve secured to the bottom of the throttle body with four screws-1MZ-FE engine shown



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Fig. Fig. 11: Be sure to discard the old IAC gasket once the throttle body and valve are separated

  1. Discard the gasket and purchase a new one.
  2.  

To install:
  1. Place the new gasket onto the throttle body.
  2.  
  3. Install the ISC valve onto the throttle body and install the four screws.
  4.  
  5. Install the throttle body into the vehicle.
  6.  
  7. Inspect the throttle linkage for freedom of movement.
  8.  

2VZ-FE and 3VZ-FE Engines

See Figure 12



Click image to see an enlarged view

Fig. Fig. 12: Exploded view of the Idle Speed Control (ISC) valve-2VZ-FE and 3VZ-FE engines

  1. Drain the engine coolant.
  2.  
  3. Disengage the ISC connector.
  4.  
  5. Disconnect the air, vacuum and coolant by-pass hoses.
  6.  
  7. Free the wire harness from the clamp; remove the retaining bolts and remove the valve with the gasket.
  8.  

To install:
  1. Install a new gasket. Install the valve and tighten the retaining bolts to 9 ft. lbs. (13 Nm).
  2.  
  3. Install the coolant by-pass hoses, the air or vacuum hoses and connect the wiring harness to the valve.
  4.  
  5. Refill the engine coolant.
  6.  

 
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