Safety Warning
DIY auto repair can cause serious injury, fire, or vehicle damage. These guides are for informational purposes only. Always follow OEM torque specs, wear PPE, and consult a certified mechanic if you are unsure. You are solely responsible for your safety.
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HOMESERVICE MANUALSGMC1999FORWARD CONTROL 5.7 R, AUTOMATICREPAIR AND DIAGNOSISEXTERNAL PAGESDIFFERENT CARSECTION 94 (ENGINE CONTROLS REMOVAL & INSTALLATION)FUEL SYSTEMS (GASOLINE ENGINES)IDLE AIR CONTROL VALVEINSTALLATION
1999 GMC Forward Control 5.7 R, Automatic
Idle Air Control Valve: Installation
1999 GMC Forward Control 5.7 R, AutomaticSECTION Installation
WARNING: This page is about a different car, the 2002 Pontiac Sunfire and 2002 Chevrolet Cavalier. However, it is still accessible from the selected car via links, so may be relevant.
CAUTION:
DO NOT manually extend or retract pintle if IAC valve has been in service, or damage to worm gear will result.
- Compare the distance between the tip, or the pintle, and the mounting flange of the new and old IAC valves. Use finger pressure to slowly retract the pintle of the new valve to the distance of the old valve. This will not cause damage to the new IAC valve but is critical for installation. If reusing IAC valve, DO NOT push or pull on pintle.
- Inspect seal for damage. Replace as necessary. Lubricate seal with clean engine oil. Install the IAC valve into the throttle body.
- Apply Thread Locking Compound (Loctite 262) onto IAC valve retaining screw threads. Tighten IAC valve retaining screw to specification. See TORQUE SPECIFICATIONS . Reconnect IAC valve harness connector. Install the air cleaner outlet resonator.
- Reset the IAC valve pintle using the following procedure:
- Turn ignition on for 20 seconds.
- Turn ignition off for 10 seconds.
- Start engine and check for proper idle operation.
- Repeat procedure if proper idle operation is not obtained.
NOTE:
Install a new screw when replacing the IAC valve.
CAUTION:
DO NOT manually extend or retract pintle if IAC valve has been in service, or damage to worm gear will result.
- Inspect "O" ring for damage. Replace as necessary. Lubricate "O" ring with clean engine oil. Install the IAC valve into the throttle body. Lubricate the IAC valve "O" ring with clean engine oil. Install the IAC valve into the throttle body.
- Apply Thread Locking Compound (Loctite 262) onto IAC valve retaining screw threads. Tighten IAC valve retaining screws to specification. See TORQUE SPECIFICATIONS . Reconnect IAC valve harness connector.
- Reset the IAC valve pintle using the following procedure:
- Turn ignition on for 20 seconds.
- Turn ignition off for 10 seconds.
- Start engine and check for proper idle operation.
- Repeat procedure if proper idle operation is not obtained.
NOTE:
Install new screws when replacing the IAC valve.
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When to See a Mechanic
Stop DIY work and contact a certified mechanic immediately if any of the following apply:
- • You smell fuel, burning insulation, or see smoke.
- • Brakes feel soft, pull hard to one side, or make grinding noises.
- • The engine overheats, stalls repeatedly, or misfires under load.
- • You are missing required tools, torque specs, or safe lifting equipment.
- • You are not confident in the next step or safety outcome.