Genuine Nissan Xterra Idle Control Valve

Nissan Xterra Idle Control Valve Parts Questions & Answers

• Valve Assembly-Aac
  23781-3S510
  Q: How to test and replace the Idle Air Control (IAC) valve on Nissan Xterra?

  A: The purpose of this study is to determine the best way to improve students' writing skills in a classroom setting. The IAC valve is what is responsible for controlling the idle speed of the engine by regulating the amount of air that goes around the throttle valve. It works with a stepper motor-type actuator, which responds to voltage pulses from PCM. The IAC valve pintle adjusts itself in response to PCM commands and this can either pull it from its seat to allow more air into or push it towards the seat to restrict airflow and hence reduce idle speed. Four-cylinder and 2002 and earlier 3.5L V6 models have a separate IAC valve mounted on the throttle body, while 2003 and later 3.5L models incorporate this function within an electronic throttle control actuator. Conversely, 3.3L V6 models feature the IAC valve located on the upper intake manifold. When testing, confirming power supply to the IAC valve should be done first thing else if anything goes wrong. This is done by disconnecting electrical connector from IAC valve; then turn ignition key On, check battery voltage at B+ wire terminal (with voltmeter). If there is no voltage present, check circuit from ignition switch to IAC valve or fuses if necessary. The IAC valve's resistance can be checked using an ohmmeter by measuring resistance across its two terminals at approximately 10 ohms resistance at 77-degrees F (25-degrees C). Replace it if resistance is not correct; otherwise, remove it for inspection on sticking or seizure of plunger. If idle issues persist while having a good condition of IAC valve then a PCM diagnostic by qualified repair facility could be needed. For these ones, there are checks that do not apply which are related to their electronic throttle control actuator in these cases rather attention shifts over to power supply assessment. Disconnect electrical connector from IAC valve; then turn ignition key On probes both B+ wires terminals to verify battery voltage at both. In case no voltage is present then examine the circuit from battery to ECCS relay, fuses, ECCS relay and circuit from ECCS relay to IAC valve. Next, use an ohmmeter to measure resistance across different pairs of terminals on the IAC valve at around 20-24 ohms at 68-degrees F (20-degrees C) for a good operating valve. Replace the IAC valve if the resistance is incorrect. If the IAC valve works fine then get PCM diagnosis from dealer service department or qualified repair facility when idle becomes problematic. During replacement, start with disconnecting battery negative terminal followed by electrical connector from IAC valve. Remove the screws attaching it and then take out IAC valve from its housing. The sealing surface of the IAC housing as well as its bore must be cleaned so as to ensure effective sealing while positioning new O-ring on housing; lubricate it with light film of engine oil. Thereafter install them together fixing them with screws and finish rest of installation in opposite order to what was done during removing process. 3.5L V6 models should have idle air volume relearn procedure performed after replacing IAC valve, albeit with different steps for 2002 and earlier models versus 2003 and later ones being available. Should idle lie outside definite parameters, look into binding throttle valve, air intake duct leakage, examine TPS or adjust closed throttle switch if necessary. Ask a professional for diagnosis if there are still problems within the system; moreover both four-cylinder engines and 3.3L V6s may feature fast idle control solenoid that maintains constant idle speed when engine load increases through engaging AC unit button (also called A/C solenoid). In order to check this system one has to warm up the motor and switch on A/C noticing slight increase in revs-per-minute (RPM), if instead the idle speed drops then test the solenoid. Disconnect electrical connector from solenoid, connect voltmeter between two terminals of harness connector, turn ignition key to ON and turn air conditioner on. Battery voltage should be indicated. In case there is no voltage present, look up possible circuit issues or air conditioning relay troubles as far as ground circuits are concerned. Consequently, turn ignition Off and apply battery voltage and ground to the solenoid terminals via jumper wires with fuses inserted, whereupon a distinct clicking sound will be heard in normal conditions. Solenoid must be replaced if it does not click. Remove it for inspection of plunger's free movement or replace bad solenoid when the plunger is seized or detent spring is damaged. Finally reconnect electrical connector and do remaining part of installation in reverse order from that of removal.