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.
1988 Chevrolet Hi-Cube 5.7 M, 475/M40FACTORY OEM SERVICE PROCEDURE
Air Control Valve
- Ensure air pump operates properly. Disconnect electrical connector at solenoid valve. Turn ignition on and check for 12 volts at connector. If voltage is not within specifications, check for open and repair as necessary.
- Start engine. Air should go to air cleaner or silencer. Connect solenoid electrical connector. Air should go to exhaust manifold. Check manifold vacuum signal at valve with engine idling. Vacuum should be 10 in. Hg (34 kPa). During decel and high vacuum signal, air should go to air cleaner and silencer. Replace valve if operation is incorrect.
Factory Service Tools
Use the Manual With the Right Hardware
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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.
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