GMC Idle Air Control (IAC) Valve Replacing?

Idle Air Control Valve is a computer-controlled air bypass valve located in the throttle body. It helps control idle speeds by allowing air to bypass the throttle plates as to increase the idle speed.

See the valve shown below:---

The procedure to replace the valve is as follows :----

OPERATION

The engine idle speed is controlled by the VCM through the Idle Air Control (IAC) valve mounted on the throttle body. The VCM sends voltage pulses to the IAC motor causing the IAC motor shaft and pintle to move in or out a given distance (number of steps) for each pulse, (called counts). This movement controls air flow around the throttle plate, which in turn, controls engine idle speed, either cold or hot. IAC valve pintle position counts can be seen using a scan tool. Zero counts corresponds to a fully closed passage, while 140 or more counts (depending on the application) corresponds to full flow.

TESTING

See Figures 1, 2 and 3

1. Disengage the IAC electrical connector.
2. Using an ohmmeter, measure the resistance between IAC terminals A and B . Next measure the resistance between terminals C and D .
3. Verify that the resistance between both sets of IAC terminals is 20-80 ohms. If the resistance is not as specified, the IAC may be faulty.
4. Measure the resistance between IAC terminals B and C . Next measure the resistance between terminals A and D .
5. Verify that the resistance between both sets of IAC terminals is infinite. If the resistance is not infinite, the IAC may be faulty.
6. Also, with a small mirror, inspect IAC air inlet passage and pintle for debris. Clean as necessary, as this can cause IAC malfunction.

Fig. Fig. 1: Test the Idle Air Control (IAC) valve resistance between A and B and terminals C and D. The resistance should be 20-80 ohms

Fig. Fig. 2: Test the Idle Air Control (IAC) valve resistance between B and C and terminals A and D. The resistance should be infinite

Fig. Fig. 3: Idle Air Control (IAC) valve wiring and terminal identification

REMOVAL & INSTALLATION

See Figures 4 through 11

Fig. Fig. 4: Unfasten the IAC valve screws and ...

Fig. Fig. 5: ... remove the IAC valve

Fig. Fig. 6: The IAC valve can be on the throttle body, usually next to the throttle position sensor-1996-97 4.3L engine shown

Fig. Fig. 7: Location of the IAC valve-1996-97 2.2L engine shown

Fig. Fig. 8: Location of the IAC valve-1998-99 2.2L engine shown

1. Disconnect the negative battery cable.
2. Remove the air cleaner assembly or resonator as necessary.
3. Unplug the electrical connection.
4. Remove the IAC valve. On thread-mounted units, use 1 ¹ / ₄ in. (32mm) wrench and on flange-mounted units, remove the screw assemblies.
5. Remove the IAC valve gasket or O-ring and discard it.

To install:

6. Clean the old gasket material from the surface of the throttle body assembly on the thread mounted valve. On the flange-mounted valve clean the surface to ensure proper O-ring sealing
7. If installing a new IAC valve, measure the distance between the tip of the valve pintle and the mounting flange. If the distance is greater than 1.10 inch (28mm), use finger pressure to slowly retract the pintle until the measurement is within specification (refer to the accompanying illustration).
8. Install the valve with a new gasket or O-ring. Tighten the thread mounted assembly 13 ft. lbs. (18 Nm) and tighten the flange mounted attaching screws to 28 inch. lbs. (3 Nm).
9. Engage the electrical connector to the IAC valve.
10. Connect the negative battery cable.

Fig. Fig. 9: When installing a new IAC valve, measure the distance between the tip of the valve pintle and the mounting flange. The distance should be 1.10 inch (28mm)

Fig. Fig. 10: Use finger pressure to slowly retract the pintle until the measurement is within specification

11. If removed, install the air cleaner or resonator.
12. On 1998-99 models to set the pintle position, turn the ignition key to the ONengine OFF for five seconds. Turn the ignition key to the OFF position for ten seconds, then start the engine and check for proper idle operation.

Fig. Fig. 11: If installing a new IAC valve, measure the distance between the valve pintle and mounting flange. If adjustment is required, use finger pressure to retract the pintle until the measurement is within specification

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This details will help you.

Thanks.

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GMC Camshaft Position (CMP) Sensor replacing?

The camshaft position sensor is a magnetic or hall effect sensor. It sends a signal to the computer relaying information about shaft speed, position and acceleration or deceleration. This information determines when the fuel/air mixture needs to be ignited and how much mixture is needed for the engine.

See all 3 sections of camshaft sensor:----
OPERATION
TESTING
REMOVAL & INSTALLATION.

OPERATION

See Figure 1

The VCM uses the camshaft signal to determine the position of the No. 1 cylinder piston during its power stroke. The signal is used by the VCM to calculate fuel injection mode of operation. If the cam signal is lost while the engine is running, the fuel injection system will shift to a calculated fuel injected mode based on the last fuel injection pulse, and the engine will continue to run.

Fig. Fig. 1: Camshaft Position (CMP) sensor location-1996-99 2.2L engines

TESTING

See Figures 2, 3, 4 and 5

Fig. Fig. 2: Typical Camshaft Position (CMP) wiring schematic-4.3L engines (wire color, terminal identification/location may vary on certain models)

1. Remove the ECM fuse to prevent the engine from starting. Removal of the ECM fuse does not disable the sensor power supply and allows testing of this sensor safely.
2. Disconnect the CMP sensor wiring harness and attach suitable jumper wires between the CMP sensor and CMP sensor harness. Connect a DC volt meter to the jumper wires corresponding to CMP IGN or PWR terminal and sensor ground.
3. With the ignition ON and the engine off, verify that the voltage is approximately battery voltage. The supply voltage should be slightly less than battery voltage.
4. If not as specified, repair or replace the fuse and/or wiring.
5. Connect a DC volt meter to the jumper wires corresponding to CMP signal terminal and sensor ground.
6. Place a socket and breaker bar or the crankshaft pulley bolt and rotate the engine slowly by hand. Observe the volt meter and verify that the voltage signal varies from approximately zero volts to slightly less than supply voltage. The voltage will switch on when the target passes the sensor and will show little or no voltage when the target is past the sensor.
7. If it is not as specified, the CMP sensor may be faulty.

Fig. Fig. 3: Common Camshaft Position (CMP) sensor wiring schematic-2.2L engines (wire color, terminal identification/location may vary on certain models)

Fig. Fig. 4: Attach suitable jumper wires between the CMP sensor and CMP sensor harness. Connect a DC volt meter to the jumper wires corresponding to IGN and sensor ground terminals and note the reading

Fig. Fig. 5: Connect the volt meter to the jumper wire corresponding to signal and sensor ground terminals, rotate the engine and observe the volt meter and verify that the voltage signal varies from approximately zero volts to slightly less than supply voltage

REMOVAL & INSTALLATION

2.2L Engines

See Figures 6 and 7

1. Disconnect the negative battery cable.
2. Raise the vehicle and support it with safety stands.
3. Remove the right hand tire assembly.
4. Unplug the sensor harness connector at the sensor.
5. Unfasten the retaining bolt, then remove the sensor from the camshaft housing.

Fig. Fig. 6: The Camshaft Position (CMP) sensor is located on the passenger side of the engine and is accessible after removing the right front tire-2.2L engine

Fig. Fig. 7: Unplug CMP sensor electrical connection and unfasten the sensor retainer, then remove the sensor from its bore in the block-2.2L engine

To install:

6. Place the sensor into position.
7. Install the CMP sensor retaining bolt, then tighten to 88 inch lbs. (10 Nm).
8. Attach the sensor harness connector.
9. Istall the tire assembly and lower the vehicle.
10. Connect the negative battery cable.

4.3L Engines

Models equipped with a distributor ignition (DI) or high voltage switch (HVS) system

The Camshaft Position (CMP) sensor is located in the distributor assembly.

1. Disconnect the negative battery cable.
2. Unplug the electrical connection from the CMP sensor.
3. Remove the distributor cap and rotor.
4. Unfasten the CMP sensor retainer(s).

If equipped, the square cut hole in the vane wheel must be aligned with the sensor in order for the sensor to be removed.

5. Remove the sensor from the distributor.

To install:

6. If equipped, line up the square cut hole in the vane wheel with the sensor and install the sensor.
7. Install the sensor and its retainers. Do not overtighten the retainers as the plastic base may strip.
8. Install the rotor and cap, then attach all necessary electrical connections.
9. Connect the negative battery cable.

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This details will help you.Thanks.

See related help solution:---

Camshaft, Bearings & Lifters Replacing on Honda Odyssey?

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