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 MANUALSCHEVROLET1987STEP VAN P20, 7.4 W, AUTOMATIC, 400/M40REPAIR AND DIAGNOSISEXTERNAL PAGESDIFFERENT CARSECTION 1 (EGR FUNCTION TESTING)EGR FUNCTION TESTINGPORTED & BACKPRESSURE EGR
1987 Chevrolet Step Van P20, 7.4 W, Automatic, 400/M40
Ported & BACKPRESSURE EGR
1987 Chevrolet Step Van P20, 7.4 W, Automatic, 400/M40SECTION Ported & BACKPRESSURE EGR
WARNING: This page does not describe the selected car, but rather 196 other vehicles, including the 1996 Chevrolet Chevy Van, 1995 Pontiac Trans Sport, 1995 Oldsmobile Silhouette, 1995 GMC Yukon, and 1995 GMC Vandura Special. However, it is still accessible from the selected car via links, so may be relevant.
- Install vacuum gauge between EGR valve and carburetor vacuum port. With engine at normal operating temperature, raise engine speed to about 3000 RPM. Vacuum gauge should read at least 5 in. Hg.
- Check EGR Thermal Vacuum Switch (TVS) operation by installing a vacuum gauge between TVS and vacuum source and noting presence of vacuum with engine running and at normal operating temperature.
- Turn engine off. Manually depress/push in EGR valve diaphragm. While depressed, hold finger over source tube and release diaphragm. Check for diaphragm and seat movement. Diaphragm should take at least 20 seconds to move to seated position. If not, replace EGR valve.
- Start engine. Using a hand-held vacuum pump, apply vacuum to EGR valve. EGR valve should open and engine should run rough or stall. If EGR valve does not open, replace EGR valve. If EGR valve opened, but idle quality did not change, clean plugged EGR ports.
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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.