Genuine Nissan Maxima Idle Control Valve

Nissan Maxima Idle Control Valve Parts Questions & Experts Answers

• IACV-Aac Valve
  23781-2Y011
  Q: What is the purpose of the Idle Air Control (IAC) valve and how can it be assessed and replaced on Nissan Maxima?

  A: The function of the Idle Air Control (IAC) valve is to regulate the idle speed of an engine by controlling the amount of air that bypasses the throttle valve. The IAC valve mounted on top of the intake plenum acts as a stepper motor actuator, and its operation is controlled by voltage pulses from the PCM. By pulling away from its seat, the pintle of the IAC valve increases intake airflow and thereby boosts idle speed while moving towards it decreases the same. To start evaluating IAC valve, inspect power supply. Disconnect electrical connector from IAC valve. Then test for battery voltage at two red wire terminals of connector. When key is on, both terminals should show battery voltage; if not check circuit from battery to ECCS relay, check ECCS relay, and check circuit from relay to IAC valve. This time, use an ohmmeter to read resistance across different pairs of terminals on specific IAC valves; at 68-degrees F (20-degrees C), there should be about 30 ohms resistance per each pair. If resistance is wrong replace IAC valve; if it reads less than 30 ohms or more than infinity then it is defective. If your vehicle has made it this far into your life without needing a PCM replacement, this may be good time to bite the bullet and have it looked at by a qualified repair shop or dealer service department because you are now running out of options as far as what could be causing it not to start when cold but run fine once warm. For replacement disconnect electrical connector from IAC valve; remove hose from IAC valve housing (1993-94 models) or remove two attaching screws (1995-later models); clean sealing surface and bore of IAC housing; position new O-ring on housing and lubricate with engine oil; then install IAC valve and tighten screws. In addition there are two fast idle control solenoids in 1995 through 2001 models which help to keep a constant idle speed during high engine loads such as when using power steering or operating the air conditioning. To test this system check if the idle speed stays constant during different conditions and inspect each solenoid by disconnecting electrical connector and use a voltmeter to measure battery voltage at specific terminals, with battery voltage present when the ignition key is on and the respective system (power steering or air conditioning) activated. Since there is no voltage look in the fuse box for that circuit and do not forget to check any fuses, you may also want to check the air conditioning clutch if applicable, air conditioning relay if applicable, Power Steering Pressure Switch, and of course ground circuits. Another quality control check would involve making sure that upon application of battery voltage and ground using fused jumper wires, the solenoid clicks. Replace a solenoid that does not click; replace one that has a seized plunger or broken detent spring. For replacement disconnect electrical connector from fast idle control solenoid; remove solenoid from IAC valve housing using wrench; install new copper washer; tighten solenoid securely. Finally in 1995 and later models there is fast idle cam and thermo element that raise idle speed during cold conditions. Based on engine temperature, thermo element plunger position adjusts fast idle cam to control idle speed. To check out this system start by disconnecting electrical connector from engine coolant temperature sensor; then connect an ohmmeter across the two terminals of sensor. Consequently start engine while watching resistance change as it warms up with coolant temperature. Marks corresponding with the center of cam follower lever pin should align with specific ranges of resistance falling within them on fast idle cam when these marks don't line up correctly adjust fast idle cam via adjustment screw. However, if your cam doesn't act properly or cannot be adjusted properly, chances are, you may need to replace the throttle body.