Suzuki Samurai/Sidekick/Tracker 1986-1998 Repair Guide

Idle Air Control (IAC) Valve

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Only the 1992-98 1.6L and 1.8L engines are equipped with an Idle Air Control (IAC) valve.

OPERATION



The purpose of the Idle Air Control (IAC) valve is to control engine idle speeds while preventing stalling due to changes in engine load. The IAC valve performs four important functions, namely:



To maintain specified engine idle speed at all times.
 
To improve engine starting.
 
To compensate the air/fuel mixture ratio during deceleration (dash-pot effect).
 
To improve driveability when the engine is at normal operating temperature.
 

The IAC assembly, mounted on the right side of the throttle body, controls bypass air around the throttle plate. By extending or retracting a conical valve, a controlled amount of air can move around the throttle plate. If engine speed (rpm) is too low, more air is diverted around the throttle plate to increase engine speed.

During idle, the proper position of the IAC valve is calculated by the ECM based on battery voltage, coolant temperature, engine load and engine speed. If the engine speed drops below a specified rate with the throttle plate closed, the ECM will then calculate a new valve position.

On 1.6L engines, four different possible designs of the IAC conical valve may be used on these engines. The first design utilizes a single taper shape, while the second design uses a dual taper shape. The third design uses a blunt-tipped valve, whereas the fourth design uses a rotating shutter. Care should be taken to ensure use of the proper design when service replacement is necessary.

TESTING



1992-98 1.6L Engines
TFI MODELS
  1. Perform a visual inspection of the valve connector to ensure it is properly engaged. Inspect the connector to ensure there are no bent, corroded, loose or damaged terminals.
  2.  
  3. Detach the wiring harness from the IAC valve connector.
  4.  
  5. Connect the positive lead of a Digital Volt-Ohmmeter (DVOM), set on the voltmeter function, to the wiring harness connector terminal 2, and the negative lead to a good engine ground.
  6.  
  7. Turn the ignition switch ON , and measure the amount of voltage from terminal 2. The proper amount of voltage should be 8.5-9.5 volts. If the voltage measured at terminal 2 is not within the specified range, there is a malfunction in the IAC valve circuit or in the ECM.
  8.  
  9. Turn the ignition switch OFF .
  10.  
  11. Switch the DVOM to the ohmmeter setting, then connect the DVOM leads to terminals 1 and 2 of the IAC valve.
  12.  
  13. Measure the IAC valve resistance, which should be 11-14 ohms at 68°F (20°C). If the resistance is not within the specified range, replace the valve with a new one. If the resistance is within the specified range, the IAC valve is functioning properly.
  14.  

MFI MODELS
  1. Perform a visual inspection of the valve connector to ensure it is properly engaged. Inspect the connector to ensure there are no bent, corroded, loose or damaged terminals.
  2.  
  3. Detach the wiring harness from the IAC valve connector.
  4.  
  5. Connect the leads of a Digital Volt-Ohmmeter DVOM, switched to the ohmmeter setting, to terminals 1 and 2 of the IAC valve.
  6.  
  7. Measure the IAC valve resistance, which should be 11-14 ohms at 68°F (20°C). If the resistance is not within the specified range, replace the valve with a new one. If the resistance is within the specified range, the IAC valve is functioning properly.
  8.  
  9. If the resistance value was within the specified range, connect a fused jumper wire between IAC valve terminal 2 to the positive battery terminal, and another jumper wire between terminal 1 and a good engine ground. With both jumper wires connected, air should be able to pass through the intake hose at the top of the valve. If air does not pass freely, the valve is defective.
  10.  
  11. If the valve is functional, check the IAC valve circuits back to the ECM for continuity.
  12.  
  13. If the IAC valve circuit checks out to be fine, the ECM may be defective.
  14.  

1.8L Engine

See Figure 1

  1. Attach a tachometer to the engine, according to the manufacturer's instructions.
  2.  
  3. Start the engine and allow it to reach normal operating temperature.
  4.  
  5. Turn the ignition switch OFF .
  6.  
  7. Remove any component necessary to gain access to the ECM.
  8.  
  9. Detach ECM E33-24 terminal from the ECM connector.
  10.  
  11. Start the engine and check the engine idle speed.
  12.  
  13. With the ignition switch ON , reattach E33-24 terminal to the ECM connector.
  14.  
  15. With the ignition switch OFF , use a jumper wire to ground E33-24 terminal of the ECM connector to a good chassis ground.
  16.  



Click image to see an enlarged view

Fig. Fig. 1: With the ignition switch turned OFF, use a jumper wire to ground ECM terminal E33-24

  1. Start the engine and recheck the engine idle speed. The idle speed should now be higher than the idle speed registered in Step 6.
    1. If the idle speed results are as described, the IAC valve and its circuit are in good condition.
    2.  
    3. If the idle speed results were not as described, jump to the next step.
    4.  

  2.  
  3. With the ignition switch OFF , detach the wiring harness connector from the IAC valve.
  4.  
  5. Use a Digital Volt-Ohmmeter (DVOM), switched to the ohmmeter setting, to measure the resistance between the two IAC valve terminals. The IAC valve resistance should be 11-14 at 68°F (20°C).
    1. If the resistance is within the specified range, proceed to the next step.
    2.  
    3. If the IAC valve resistance was not within the specified range, replace the IAC valve with a new one.
    4.  

  6.  
  7. With the IAC valve disconnected from the wiring harness, start the engine and observe the idle speed registered on the tachometer.
  8.  


WARNING
If the battery is connected to the wrong IAC valve terminals, the valve will be damaged beyond repair.

  1. While the engine idles, attach a 12 volt DC battery to the two IAC valve terminals as shown in the accompanying illustration. Recheck the idle speed, which should now be higher than measured in Step 12.
    1. If the idle speed in Step 13 is higher than that of Step 12, inspect the IAC valve circuit for problems.
    2.  
    3. If the idle speed in Step 12 is higher than that registered in Step 13, replace the IAC valve with a new one.
    4.  

  2.  

REMOVAL & INSTALLATION



1992-98 1.6L Engines
TFI MODELS
  1. Disconnect the negative battery cable.
  2.  
  3. Disengage the wiring harness connector from the IAC valve.
  4.  
  5. Remove the EGR modulator from its mounting bracket.
  6.  
  7. Detach the fast idle valve hose from the IAC valve.
  8.  
  9. Drain the engine coolant into a large catch pan.
  10.  
  11. Remove the two clamps, then detach the two engine coolant hoses from the IAC valve.
  12.  
  13. Remove the IAC valve mounting bolts, then separate the valve from the throttle body.
  14.  

To install:
  1. Clean the IAC valve gasket mating surface, then install a new gasket.
  2.  
  3. Place the IAC valve assembly into position, then install and tighten the mounting screws to 44 inch lbs. (5 Nm).
  4.  
  5. Install the two engine coolant hoses and clamps to the IAC valve.
  6.  
  7. Reattach the fast idle valve hose to the IAC valve.
  8.  
  9. Attach the wiring harness connector to the valve.
  10.  
  11. Connect the negative battery cable.
  12.  
  13. Refill the cooling system with the proper amount and type of engine coolant.
  14.  
  15. Start the engine and verify proper IAC valve operation. Check for engine coolant leakage.
  16.  

MFI MODELS
  1. Disconnect the negative battery cable.
  2.  
  3. Drain the engine coolant into a large catch pan.
  4.  
  5. Remove the throttle cover mounting bolts, then remove the cover from the throttle body.
  6.  
  7. Remove the IAC valve air intake hose, then detach the wiring harness connector from the valve.
  8.  
  9. Disconnect the engine coolant hoses from the IAC valve.
  10.  
  11. Remove the mounting fasteners, then separate the IAC valve from the throttle body.
  12.  

To install:
  1. Clean the IAC valve gasket surfaces thoroughly, then install a new gasket on the IAC valve.
  2.  
  3. Position the valve on the throttle body, then install the mounting bolts. Tighten the bolts to 13.5-20.0 ft. lbs. (18-28 Nm).
  4.  
  5. Reattach the engine coolant hoses, the wiring harness connector and the air intake hose to the IAC valve.
  6.  
  7. Install the throttle cover, and secure it on the engine with the three retaining bolts.
  8.  
  9. Connect the negative battery cable.
  10.  
  11. Fill the engine cooling system.
  12.  
  13. Start the engine and inspect for coolant leaks. Ensure that the IAC valve functions properly.
  14.  

1.8L Engine
  1. Disconnect the negative battery cable.
  2.  
  3. Disengage the wiring harness connector from the valve.
  4.  
  5. Remove the mounting fasteners, then separate the IAC valve from the intake manifold.
  6.  

To install:
  1. Clean the IAC valve gasket surfaces thoroughly, then install a new gasket on the IAC valve.
  2.  
  3. Position the valve on the intake manifold, then install the mounting bolts.
  4.  
  5. Reattach the wiring harness connector to the IAC valve.
  6.  
  7. Connect the negative battery cable.
  8.  
  9. Start the engine and ensure that the IAC valve functions properly.
  10.  

 
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