How to test idle air control valve？
First, we need to know what does the idle air control valve do.
The idle air control valve is powered by the ignition switch, as long as the ignition switch is turned to the ON position, the idle air control valve is energized and the engine computer controls its circuit override. When the engine operating parameters deviate from the normal value, the valve is used to adjust the idling speed. It is used for the opening of the bypass air passage of the EFI system to adjust the bypass air volume so that the engine speed reaches the required target value.
To ensure proper idle performance, it is important to understand how the idle air control system works and how to perform idle air control valve detection when problems occur.
First, idle air control system on the car test
(1) engine idling condition detection
After starting the engine in the cold state, when the warm-up process begins, the idling speed of the engine should reach the specified fast idling speed (usually 1500r/min); after the engine reaches the normal working temperature, the idling speed should return to normal (usually 750r/min). If the idle speed cannot change according to the above rule after cold start, the idle air control system is faulty.
After the engine reaches the normal working temperature, the engine idle speed should rise to about 900r/min when the air conditioning switch is turned on. If the engine speed drops after opening the air conditioning switch, the idle air control system is faulty.
In the engine idling, if the idle speed adjusting screw for micro rotation, the engine idle speed should not change (after rotation should make the idle speed adjusting screw back to the original position). If the idle speed changes in the rotation, the idle air control system does not work.
(2) idle air control valve working condition check
For the pulse linear solenoid valve idle control valve, can be unplugged in the engine idle air control valve harness connector, observe whether the engine speed change. When the engine speed changes, the idle air control valve works normally.
For the stepper motor idle air control valve, listen to the idle air control valve in a moment after the engine is turned off whether there is a “buzzing” working sound (at this time the stepper motor should work until the idle air control valve is completely open, in order to facilitate the engine to start again). If the idle air control valve makes a “humming” sound, the idle air control valve is good.
In order to check the working condition of the stepper motor idle air control valve, you can also unplug the idle air control valve harness connector before the engine starts, and then plug it in after the engine starts, and observe whether there is a change in the engine speed. If the engine speed changes at this time, the idle air control valve is working properly; otherwise, the idle air control valve or control circuit is faulty.
(3) ECU control voltage detection
For the pulse linear solenoid valve idle control valve, should unplug the idle control valve harness connector, use the multimeter voltage file to measure the terminal voltage.
If in the engine running process, idle control valve harness connector terminal pulse voltage output, ECU and idle control system line without fault. If there is no pulse voltage output, turn on the air conditioning switch and then test. If there is still no pulse voltage output, the idle air control system does not work, should check the line between the ECU and idle air control valve (whether there is poor contact or broken circuit fault); if the line of the idle speed system is not faulty, the ECU is faulty, should replace the ECU.
For stepper motor idle control valve, put the ignition switch in “ON” position, and then measure the voltage value between terminals ICS1, ICS2, ICS3, ICS4 and terminal E1 of ECU (should be 9-14V), if there is no voltage, the ECU is faulty.
Second, the idle air control valve detection
(1) Idle air control valve coil resistance detection
Remove the idle air control valve and measure the resistance value of the idle air control valve coil with a multimeter Ω file (Figure 2).
Pulse linear solenoid valve idle air control valve has only one set of coil, its resistance value is 10-15Ω stepper motor idle air control valve usually has 2-4 sets of coil, the resistance value of each set of coil is 10-30Ω.
if the coil resistance value is not in the above range, the idle air control valve should be replaced.
(2) The action of stepping motor check
The battery power is fed to each coil of the stepper motor in a certain order to make the stepper motor rotate. The coil configuration and terminal arrangement of different stepper motors may vary. Here, the Crown 3.0 sedan with the 2JZ-GE engine idle control valve stepper motor is taken as an example to explain its inspection method.
First, connect the positive battery terminal to the stepper motor connector terminal B+, and then connect terminals S1, S2, S3, and S4 to the negative battery terminal in sequence. At this time, the stepper motor should rotate, and the spool should move outward.
If terminals S1, S2, S3, and S4 are connected to the negative battery terminal in the opposite order (S4, S3, S2, and S1), the stepper motor should rotate in the opposite direction, and the spool should move inward and retract.
If the stepper motor does not rotate or the spool does not move normally, it indicates that the stepper motor coil, wiring circuit, connector terminals, or internal components may have a fault. Further inspection of the idle air control valve is required to identify the cause of failure and confirm whether the valve assembly needs to be replaced. A properly functioning idle air control valve ensures accurate bypass air regulation and stable engine idle performance.
