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 MANUALSCHEVROLET1985NOVA BASE, STANDARDREPAIR AND DIAGNOSIS (SINGLE PAGE)ENGINE PERFORMANCESYSTEMEGR SYSTEM - GASOLINECOMPONENT TESTINGPOSITIVE BACKPRESSURE EGR VALVE
1985 Chevrolet Nova Base, Standard
Positive BACKPRESSURE EGR Valve
1985 Chevrolet Nova Base, StandardSECTION Positive BACKPRESSURE EGR Valve
- Disconnect electrical connector from EGR solenoid. Place transmission in Neutral (man. trans.) or "P" (auto. trans.). Set parking brake and block drive wheels. Connect tachometer to engine.
- Ensure that fast idle speed is set to specified RPM. With engine at normal operating temperature, place fast idle screw on highest step of fast idle cam.
- Disconnect and plug vacuum hose at EGR valve. As vacuum hose is removed, watch for downward movement of diaphragm. This should be accompanied by an increase in engine speed.
- Reconnect vacuum hose. Diaphragm should move upward and engine speed should decrease.
- If engine speed change and diaphragm movement are noticed with vacuum hose removed or installed, EGR valve is operating properly. Reconnect electrical connector to EGR solenoid.
- If engine speed and diaphragm movement did not occur, remove EGR valve from engine. Connect a vacuum pump to EGR valve and apply a constant vacuum of 10 in. Hg. EGR valve should not open. If EGR valve does open, replace it.
- With vacuum still applied to EGR valve, direct a 15 psi air pressure stream directly into valve seat. EGR valve should open fully. If not, EGR valve should be cleaned.
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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.