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 145 (ENGINE CONTROL SYSTEM - SYSTEM & COMPONENT TESTING)EMISSION SYSTEMS & SUBSYSTEMSPOSITIVE CRANKCASE VENTILATIONINSPECTION/DIAGNOSIS
1999 GMC Forward Control 5.7 R, Automatic
Positive Crankcase Ventilation: Inspection/Diagnosis
1999 GMC Forward Control 5.7 R, AutomaticSECTION Inspection/Diagnosis
WARNING: This page is about a different car, the 2003 Pontiac Vibe. However, it is still accessible from the selected car via links, so may be relevant.
WARNING:
Do not breathe the air through the EVAP component tubes or hoses. The fuel vapors inside the EVAP components may cause personal injury.
- Blow air into the cylinder head side of the PCV valve.
- Check that air passes through the PCV valve easily.
- Blow air into the intake manifold side of the PCV valve.
- Check that air passes through the PCV valve with high resistances.
- If the PCV valve fails either test, replace the PCV 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.