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 MANUALSFORD1991AEROSTAR VAN CARGO EXTENDED, 4.0 X, AWDREPAIR AND DIAGNOSIS (SINGLE PAGE)ENGINE PERFORMANCESYSTEMEGR FUNCTION TESTINGTESTINGPORTED EGR VALVE
1991 Ford Aerostar Van Cargo Extended, 4.0 X, AWD
Ported EGR Valve
1991 Ford Aerostar Van Cargo Extended, 4.0 X, AWDSECTION Ported EGR Valve
- Check vacuum hoses for correct routing. Connect a vacuum gauge directly to EGR vacuum source. With engine running, open throttle. If gauge indicates vacuum, EGR vacuum supply is okay.
- If gauge indicates no vacuum, EGR vacuum port is plugged. Disconnect vacuum hose at EGR valve, and plug hose. Connect a vacuum pump to EGR valve.
- Start engine. Apply 6-10 in. Hg to EGR valve. Engine should run rough or stall and EGR valve should hold vacuum. If engine speed does not change, check for plugged EGR passages or faulty EGR 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.