What is an IAC valve? - 1992 Toyota Paseo

What is year--make--model? Any applicable trouble codes? So your having trouble with idle? Remove throttle body, clean throttle bore and any small passages. Check and clean anything that has to do with idle air system.

Possible causes
- Faulty Idle Air Control (IAC) valve
- Idle Air Control (IAC) valve harness is open or shorted
- Idle Air Control (IAC) valve circuit poor electrical connection
What does this mean? Tech notes
The P1507 code means that the engine idle is out of factory specification. Sometimes the Idle Air Control (IAC) may have carbon built up. Disconnect the car battery, remove the valve, clean, re-install valve, and drive the vehicle for about 5 minutes with the headlights and A/C ON to get the idle relearned.
If the problem persist, the IAC valve may need to be replaced.

Read more: http://www.engine-codes.com/p1507_ford.html#ixzz3sFPyZe00

Here you go: 2000 3.2TL - DTC Troubleshooting: P1519 (14)

DTC P1519: IAC Valve Circuit Malfunction

1. Reset the PCM.
   

2. Turn the ignition switch ON (II).
   
   Is DTC P1519 indicated? YES -

   Go to step 3.
   NO -

   Intermittent failure, system is OK at this time. Check for poor connections or loose wires at the IAC valve and the PCM.n
   

1. Turn the ignition switch OFF.
   

2. Disconnect the IAC valve 3P connector.
   

3. Turn the ignition switch ON (II).
   

1. Measure voltage between IAC valve 3P connector terminal No. 2 and body ground.
   
   Is there battery voltage? YES -

   Go to step 7.
   NO -

   Repair open in the wire between the IAC valve and the PGM-FI main relay.n
   

1. Turn the ignition switch OFF.
   

1. Check for continuity between body ground and IAC valve 3P connector terminal No. 1.
   
   Is there continuity? YES -

   Go to step 9.
   NO -

   Repair open in the wire between the IAC valve and G101.n
   

1. Disconnect PCM connector B (25P).
   

1. Check for continuity between body ground and PCM connector terminal B23.
   
   Is there continuity? YES -

   Repair short in the wire between the IAC valve and the PCM (B23).n
   NO -

   Go to step 11.
   

1. Connect IAC valve 3P connector terminal No. 3 to body ground with a jumper wire.
   

1. Check for continuity between PCM connector terminal B23 and body ground.
   
   Is there continuity? YES -

   Go to step 13.
   NO -

   Repair open in the wire between the IAC valve and the PCM (B23).n
   

1. Remove the jumper wire from the IAC valve 3P connector, then reconnect the IAC valve 3P connector.
   

2. Turn the ignition switch ON (II).
   

1. Measure voltage between body ground and PCM connector terminal B23.
   
   Is there battery voltage? YES -

   Substitute a known-good PCM and recheck. If the symptom/indication goes away, replace the original PCM.n
   NO -

   Replace the IAC valve.n
   

Disconnect the negative cable from the battery terminal...Locate the IAC valve on the side of the engine, near the intake...Remove the electric cable on the back of the IAC valve. Remove the screws that attach to the IAC valve and set them aside...
Pull the IAC out of the Cadillac DeVille and replace with new valve...Connect the IAC valve to the wire and reconnect the screws. Turn the screws so that they are completely tightened...Reconnect the negative cable to the battery and start engine to test valve.

Good luck, i hope this helps.

Operation

The Idle Air Control (IAC) valve controls the amount of air that bypasses the throttle valve, which controls the engine idle speed. The IAC valve consists of windings, an armature, a return spring, and a rotary slide. The engine control module (ECM) pulses the voltage to the winding, the opposing forces on the armature by the return spring cause it to maintain a fixed position, adjusting the amount of bypass air to maintain the correct idle speed.

Removal & Installation

1. Turn the ignition switch to the OFF position.
2. Disconnect the idle air control valve harness electrical connector.
3. Using a suitable tool, remove idle air control valve.
4. Installation is in reverse order of removal.

Testing

Checking Idle Air Control Valve (IAC) Triggering

1. Check IAC valve is electrically OK.
2. Slide up boot on the IAC valve connector.

Fig. IAC Connector

1. Use scan tool 'Output Diagnostic Test Mode' function 03 to trigger the IAC valve - N71.
2. Connect VAG 1527B voltage tester, or equivalent, between terminal 1 and engine ground (GND). Voltage tester must flash.
3. Connect VAG 1527B voltage tester, or equivalent, between terminal 2 and battery positive voltage (B+). Voltage tester must light up.
4. If specified results are not obtained:
   1. Connect VAG 1598/19 test box, or equivalent, to ECM harness connector.
   2. Check the wiring between harness and connector terminal 1 (in engine compartment) to test box socket D11 . Then check the wiring between harness connector terminal 2 and test box socket D9 using wiring diagram. Repair as necessary.
   3. If the wiring is okay, but triggering still does not occur, replace the ECM.
   4. If the triggering signal and the wiring are okay and the valve does not react, replace the IAC valve.
   
   

Checking Mechanical Function

1. Remove the idle air control (IAC) valve.
2. Visually check the surface of the rotary slide (arrow) for signs of wear.

Fig. Showing the IAC Valve

WARNING Do NOT check for ease of movement by prying on the rotary slide with a screwdriver or other tools that could cause scratching or other damage.

1. Reconnect the IAC valve, while still removed, to the harness connector.
2. Use scan tool 'Output Diagnostic Test Mode' function 03 to trigger IAC valve - N71.
3. Check whether rotary slide moves freely from stop to stop.
4. If there are signs of scoring, or if the rotary slide does not move freely in both directions, replace the IAC valve.
5. If the IAC valve does not respond (not triggered) during the Output Diagnostic Test Mode, check triggering.

Resistance Test

1. Remove the idle air control valve harness connector.
2. Use a suitable Digital Multimeter (DMM) to measure the resistance between the 2 terminals of the idle air control valve.
3. The correct measurement should be 7-11 ohms. If not, replace the idle air control valve.

NOTE At room temperature, the resistance value will be lower. The resistance value will be higher if the Idle Air Control (IAC) valve is measured at under-hood operating temperatures.

1. Reconnect the idle air control valve harness connector.
2. The idle air control valve should hum and vibrate slightly when the ignition is turned 'ON'. If not, the ECM or harness may be defective.

Testing with VAG1551:

1. Remove the idle air control valve harness connector.
2. Connect the VAG 15278 LED tester to terminals 1 and 2 of the harness connector using the jumpers from VW 1594 adaptor kit.
3. Turn ignition ON, perform steps from output DTM (Diagnostic Test Mode) to activate the IAC valve (N71) LED tester must blink.
4. If tester does not blink, check wiring using VAG 1598 pin out box, electrical checks, step 26. Repair as necessary.
5. If wiring is okay, replace the ECM.
6. If LED tester blinks but the IAC valve does not operate, replace the IAC valve.

Get the IAC valve checked.Remove the Iac valve from the throttle body. It is on the side facing the front higher than the tps sensor. It has a 4 wire connector. Make sure this is clean. If it is dirty/dusty then clean it. This valve controls the idle speed. After cleaning it turn the ignition on with the engine off. The Iac should move in and out to find the stops. If it does not move you have either bad wiring, Iac or pcm. Most likely is Iac.
-------- For safety measures,before removing the IAC make sure you don't have any vacuum hoses unplugged. Next make sure the throttle blade closes all the way.Iac is short for idle air control valve. ------- Thanks.Helpmech.

change the idle air control valve.

Idle Air Control (IAC) Valve OPERATION The Idle Air Control (IAC) valve controls the engine idle speed and dashpot functions. The valve is located on the side of the throttle body. This valve allows air, determined by the Powertrain Control Module (PCM) and controlled by a duty cycle signal, to bypass the throttle plate in order to maintain the proper idle speed. Fig. 1: Typical Idle Air Control (IAC) valve which is mounted to the throttle body - cutaway view shows air bypass direction
--- REMOVAL & INSTALLATION

1. Disconnect the negative battery cable. To remove the IAC valve, first disconnect the negative battery cable, then the IAC wire harness plug
   Next, remove the two IAC valve attaching bolts . . .
   . . . and pull the valve from the intake manifold
   
   
2. Disengage the wiring harness connector from the IAC valve.
3. Remove the two retaining screws, then remove the IAC valve and discard the old gasket. To install: When installing the valve, always discard the old gasket and install it using a new one
   
   
4. Clean the IAC valve mounting surface on the throttle body of old gasket material.
5. Using a new gasket, position the IAC valve on the throttle body. Install and tighten the retaining screws to 71-106 inch lbs. (8-12 Nm).
6. Attach the wiring harness connector to the IAC valve.
7. Connect the negative battery cable.

you need to clean your idle air control valve ( or replace it) Spray carb cleaner does a nice job of cleaning it.

This tutorial is from autozone.com

OPERATION

The Idle Air Control (IAC) is a bi-directional motor driven by two coils. The purpose of the IAC valve is to control engine idle speed, while preventing stalls due to changes in the engine load. The IAC valve, mounted in the throttle body, controls bypass air around the throttle plate. The PCM controls engine idle speed by adjusting the position of the IAC motor pintle. The PCM pulses current to the IAC coils in small steps (counts) to extend the pintle into a passage in the throttle body to decrease air flow. The PCM reverses the current pulses to retract the pintle, increasing air flow. This method allows highly accurate control of idle speed and quick response to changes in engine load. If RPM is too low, the PCM will retract the IAC pintle, resulting in more air being bypassed around the throttle plate to increase RPM. If the RPM is too high, the PCM will extend the IAC pintle, allowing less air to be bypassed around the throttle plate, decreasing RPM.

Fig. Typical Idle Air Control (IAC) valve components
During idle, the proper position of the of the IAC pintle is calculated by the PCM based on the battery voltage, coolant temperature, engine load and engine RPM. If the RPM drops below a specified value, and the throttle plate is closed (TP sensor voltage is between 0.20-0.74), the PCM senses a near stall condition. The PCM will then calculate a new IAC pintle position to prevent stalls.
If the IAC valve is disconnected and reconnected with the engine running, the idle RPM will be wrong. In this case, the IAC has to be reset. The IAC resets when the ignition switch is cycled ON and then OFF . When servicing the IAC, it should be disconnected or connected with the ignition switch OFF in order to keep from having to reset the IAC valve.
The position of the IAC pintle affects engine start up and the idle characteristics of the vehicle. If the IAC pintle is fully open, too much air will be allowed into the manifold. This results in high idle speed, along with possible hard starting and a lean air/fuel ratio. A Diagnostic Trouble Code (DTC) may set. If the IAC pintle is stuck closed, too little air will be allowed in the manifold. This results in a low idle speed, along with hard starting and a rich air/fuel ratio. Again, a Diagnostic Trouble Code (DTC) may set. If the IAC pintle is stuck part way open, the idle may be high or low and will not respond to changes in engine load.

TESTING

As with most all engine control sensors used in your vehicle, a thorough and proper test can only be performed by a qualified technician using a scan tool to read the data stream from the PCM. There are a few items a non-professional should check before taking the vehicle to a qualified technician for diagnosis and repair.

Check for a poor connection at the PCM or IAC motor. Inspect the harness connectors for backed out terminals, improper mating, broken locks, improperly formed or damaged terminals and poor terminal-to-wire connection. Inspect for a damaged wiring harness, especially if heavy work has recently been performed (intake manifold removal, engine removal, etc.) where the throttle body has been disturbed. Inspect for a restricted air intake system. Check for a possible collapsed air intake duct, restricted air filter element or foreign objects blocking the air intake system. Inspect the throttle body. Check for objects blocking the IAC passage or throttle bore. Excessive deposits, especially on high-mileage engines, can build up in the IAC passage and on the IAC pintle. Excessive deposits can also build up on the throttle plate, so check for a sticking throttle plate. Check for vacuum leaks such as disconnected hoses, leaks at the EGR valve and EGR pipe to the intake manifold, leaks at the throttle body, faulty or incorrectly installed PCV valve, leaks at the intake manifold brake booster hose connection, etc.

REMOVAL & INSTALLATION

1. Disconnect the negative battery cable.
2. Detach the electrical connector from the IAC valve.
3. Remove the 2 attaching screws and remove the IAC valve from the engine. Remove the O-ring from the housing.

To install:

Fig. The Idle Air Control (IAC) valve is mounted on the throttle body-3.8L (VIN K) engine shown, others similar

NOTE Before installing a new IAC valve, measure the distance that the valve is extended. The measurement should be made from the motor housing to the end of the valve cone (pintle). The distance should be no greater than 1 1 / 8 inch (28mm). If the pintle is extended too far, adjustment is required, otherwise damage may occur when the IAC valve is installed. Adjust the IAC valve by compressing the pintle to achieve the correct length.

1. Use a new O-ring, install the IAC valve and tighten the retaining screws to 18 inch lbs. (2 Nm).
2. Attach the electrical connector.
3. Connect the negative battery cable.
4. The PCM will reset the IAC valve the next time the ignition switch is turned ON and then OFF .
5. Start the engine and allow to warm to operating temperature to check idle quality.

Hi there,

Well please follow the below link to check out the position of idle valve -

http://www.freeengineinfo.com/idle-air-control-valve-replacement.htm

The Idle Air Control (IAC) valve controls the engine idle speed and dashpot functions. The valve is located on the side of the throttle body. This valve allows the necessary amount of air, as determined by the Powertrain Control Module (PCM) and controlled by a duty cycle signal, to bypass the throttle plate in order to maintain the proper idle speed.

TESTING
Turn the ignition switch to the OFF position.
Disengage the wiring harness connector from the IAC valve .
Using an ohmmeter, measure the resistance between the terminals of the valve.

NOTE: Due to the diode in the solenoid, place the ohmmeter positive lead on the VPWR terminal and the negative lead on the ISC terminal.
If the resistance is not 7–13 ohms, replace the IAC valve.

The following symptoms can be caused by a faulty IAC due to loose connections, bad grounds, high resistance in the circuit, or opens in the circuit.
 
REMOVAL & INSTALLATION
Disconnect the negative battery cable.
Disengage the wiring harness connector from the IAC valve.
Remove the two retaining screws, then remove the IAC valve and discard the old gasket.

To install:
Clean the IAC valve mounting surface on the throttle body of old gasket material.
Using a new gasket, position the IAC valve on the throttle body. Install and tighten the retaining screws to 71–106 inch lbs. (8–12 Nm).
Attach the wiring harness connector to the IAC valve.
Connect the negative battery cable.


Good Luck!!

Thanks

its located on the throttle body connected to your air intake manifold where your throttle cable connects on the throttle body there is a adjustment screw connected there