Car idle air control valve

How to detect the idle air control valve failure

You need a multimeter to check the component serviceability. First, check that there are no breaks in the valve's power supply circuit. For this, set the gauge to the voltmeter mode, connect its negative wire to the negative terminal on the engine body, and the positive wire - to the corresponding valve terminals that are typically marked with A and D symbols. If there is no voltage, check the circuit continuity and the ECU serviceability.

Then set the gauge to the ohmmeter mode and measure resistance between the valve terminals A and B, and then - between C and D. It should be 40-80 Ohms. After that, connect the multimeter probes in pairs to terminals A and C, B and D. If the valve is in good working order, the gauge will indicate an open circuit.

You may identify that the idle air control valve needs to be diagnosed by the following symptoms:

• unstable engine rpms at idle;
• the engine stops during driving when shifting gears;
• sharp rpm decrease when the headlights or accessory equipment is switched on;
• the Check Engine indicator flashes on the instrument panel (not relevant for all vehicles);
• the engine does not gain high rpms without preheating.

Causes ofthe idle air control valve failure

The most frequent idle air control valve malfunction is breakage of the internal wires. Usually it results from the moisture and dirt impact on the part components. The valve contacts can become oxidized, which prevents the uninterrupted passage of the electrical signal as well. Accumulation of dirt, formation of carbon and oil deposits eventually result in jamming of the tapered needle, due to which the valve can no longer regulate the air supply bypassing the throttle valve. If you encounter this problem too often, check the oil level, the valve stem seals state, and check whether the crankcase ventilation line is not clogged.

In some cases incorrect functioning of the idle air control valve or its complete failure result from the insufficiently reliable fastening of the wire harness connector in the component housing, or a shorted power circuit.

Sometimes, the guides of the tapered needle or parts of its actuator may wear out. In such a case, the valve requires replacement.

Repairofthe idle air control valve

You can repair the idle air control valve only if its malfunctions occur due to contamination. For this, the part must be removed from the car and thoroughly cleaned with a special agent and a dry soft cloth. If there is too much contamination, be sure to examine the throttle assembly internal surface: most likely, it requires cleaning as well.

Replacement ofthe idle air control valve

You can easily replace the part on your own. For this, adhere to the following procedure:

1. Disconnect the negative terminal from the battery.
2. Pull out the connector of the wire going from the throttle intake to the valve, after releasing the lock.
3. Unscrew the valve fastening screws and remove it.
4. Install a new part, following the sequence in reverse order.
5. Perform the idle air control valve adjustment. For this, connect the negative terminal to the battery and switch on the ignition for 5-10 seconds without starting the engine. All required adjustments will be made automatically.