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 MANUALSCHEVROLET1989CAPRICE BASE, 4.3 Z, 700R4/MD8REPAIR AND DIAGNOSIS (SINGLE PAGE)ENGINE PERFORMANCESYSTEMEGR SYSTEMCOMPONENT TESTINGPULSE WIDTH MODULATED EGR VALVE
1989 Chevrolet Caprice Base, 4.3 Z, 700R4/MD8
Pulse Width Modulated EGR Valve
1989 Chevrolet Caprice Base, 4.3 Z, 700R4/MD8SECTION Pulse Width Modulated EGR Valve
- Check vacuum lines for leaks and electrical connectors for proper installation. Place transmission in Park or Neutral. With engine at normal operating temperature and engine idling, push up on underside of EGR valve diaphragm. Engine RPM should drop. If engine RPM does not drop, clean EGR valve and passages.
- Check for EGR valve diaphragm movement with engine RPM change from 2000 RPM to idle. EGR valve diaphragm should not change. If EGR valve diaphragm moves with RPM change, check Park/Neutral switch for open circuit or misadjustment. If EGR valve diaphragm does not move, disconnect ALDL "test" connector and ground test terminal. If EGR valve diaphragm moves, EGR valve is functioning properly.
- If EGR valve diaphragm still does not move, stop engine and disconnect EGR solenoid connector. Connect 12-volt test light between EGR solenoid connector terminals. Turn ignition on and ground ALDL "test" terminal. Test light should flash repeatedly.
- If test light flashes, check for vacuum to EGR solenoid at 2000-3000 RPM. If engine does not use a vacuum regulator, there should be at least 7 in. Hg vacuum at solenoid. If engine is equipped with a vacuum regulator, there should be 2-10 in. Hg vacuum.
- If vacuum is greater than 10 in. Hg, replace regulator. If vacuum is less than 2 in. Hg, vacuum at solenoid is okay and check EGR solenoid connections and/or faulty EGR solenoid. See appropriate C-7 CHART in the COMPUTERIZED ENGINE CONTROLS section for further diagnosis.
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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.