General information
When the engine is idling, the composition of the air-fuel mixture is controlled by the idle speed stabilization system (IAC). On Civic models, the system consists of a PCM and an IAC valve, on Integra models it consists of a PCM, a temperature-sensitive fast idle speed valve (FIT) and IAC valves. The activation of the IAC valve is made by the command of the ECM / PCM, depending on the current load on the engine (turning on the air conditioner, using the power steering, unit temperature, etc.). the valve regulates the amount of air flow supplied to the intake manifold bypassing the throttle valve. The ECM / PCM receives initial data from the VSS, ECT sensors, PSP sensor-switches and the operation of the A/C compressor clutch. Depending on the current load on the engine, the module adjusts its idle speed accordingly. To prevent idle stability when starting the engine, the IAC valve opens during cranking and remains open for some time immediately after starting, allowing additional air to enter the intake manifold.
Examination
1. Engage the parking brake, chock the vehicle's wheels, and shift the transmission into neutral (RKPP) or in position "R" (AT). Connect a tachometer to the engine according to the manufacturers instructions. Start the engine and raise its speed to 3000 rpm. Wait for the cooling fan to operate, then idle to idle and disconnect the IAC valve electrical connector.
Attention! Avoid touching the fan blades with your hands and avoid getting hair or loose clothing in contact with them. When the valve is disconnected, a noticeable decrease in engine speed should occur, otherwise the valve is most likely defective. If there is a drop in revs and the problem persists, check the condition of the wiring harness and its contact connections in the area between the IAC valve and the ECM/PCM.
2a. Disconnect the wiring from the IAC valve, turn on the ignition (do not start the engine) and measure the voltage between the positive terminal of the connector on the harness side (yellow-black wire terminal) and body weight (see accompanying illustrations): Civic models. The voltmeter should register the battery voltage. If there is no voltage, check the condition of the yellow/black wiring harness between the IAC valve and the PGM-FI main relay. In any case, leave the connector disconnected for further checks.
2b. Valve model Integra.
3. If the IAC wiring harness has two wires, connect the valve with two jumper wires directly to the battery (a black-yellow wire is connected to the positive terminal, a black-blue wire to the negative terminal). The valve should make a click every time power is applied.
Attention! Do not keep the valve energized longer than necessary to hear the click!
4. If the harness consists of three wires, connect the negative ohmmeter probe to the center terminal of the connector, and the positive probe to each of the side terminals in turn. In both cases, the device must register a resistance of 16÷28 ohms.
5. If the results of the checks set out in paragraphs 3 and 4 are positive, the car should be driven to a workshop for a more detailed diagnosis of the condition of the ECM / PCM and the IAC valve circuit.
Replacement
1. Disconnect the electrical wiring from the IAC valve.
2. Remove the two fixing screws and remove the sensor from the air path pressure chamber (see illustrations above).
3. Installation is carried out in the reverse order. Don't forget to replace the o-ring.