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 VALVECLEANING & INSPECTION PROCEDURE
1999 GMC Forward Control 5.7 R, Automatic
Cleaning & Inspection Procedure
1999 GMC Forward Control 5.7 R, AutomaticSECTION Cleaning & Inspection Procedure
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.
If using the original IAC valve, perform the following inspection and cleaning procedure:
- Clean the IAC valve sealing surface, pintle valve seat and air passage in the throttle body.
- Whenever the air passages have heavy deposits, remove the throttle body for a complete cleaning. See THROTTLE BODY .
- The IAC valve may be cleaned by using a shop towel or small parts cleaning brush to remove heavy deposits.
- Shiny spots on the pintle or seat are normal, and not an indication of a misaligned pintle shaft.
- Inspect the IAC valve seal for cuts, cracks or distortion. Replace the IAC valve if the valve is damaged.
If using the original IAC valve, perform the following inspection and cleaning procedure:
- Clean the IAC valve "O" ring sealing surface, the pintle valve seat, and the air passage.
- The IAC valve may be cleaned using a shop towel or a parts cleaning brush to remove heavy deposits.
- Shiny spots on the pintle or seat are normal, and do not indicate misalignment or a bent pintle shaft.
- Whenever the air passages have heavy deposits, remove the throttle body for a complete cleaning. See THROTTLE BODY .
- Inspect the IAC valve "O" ring for cuts, cracks or distortion. Replace the IAC valve if the valve is damaged.
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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.