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 MANUALSHYUNDAI1991SONATA V6-3.0LREPAIR AND DIAGNOSISPOWERTRAIN MANAGEMENTEMISSION CONTROL SYSTEMSEXHAUST GAS RECIRCULATIONTESTING AND INSPECTIONFEDERALCOMPONENT TESTS
1991 Hyundai Sonata V6-3.0L
Component Tests
1991 Hyundai Sonata V6-3.0LSECTION Component Tests
EGR VALVE
1. Remove the EGR valve and check it for sticking and excess carbon deposits.
2. Connect a manual vacuum pump to the EGR valve.
3. Apply a vacuum of 67 kPa (20 in. Hg) and verify that the diaphragm chamber is air tight.
4. Apply 7 kPa (2 in. Hg) of vacuum to the EGR valve and verify that air will not pass through the valve.
5. Increase the vacuum applied to 23 kPa (7 in. Hg) and verify that air will pass through the EGR valve. If any of the tests in steps 3 through 5 failed, replace the EGR valve.
6. After testing or replacing the EGR valve, replace the gasket and tighten the mounting bolts to 19-28 Nm (14-20 ft. lbs.).
Vacuum Testing The Thermo Valve:
THERMO VALVE
1. Disconnect the vacuum hoses from the thermo valve and connect a manual vacuum pump to the thermo valve.
2. Apply a vacuum and verify that when engine coolant temperature is less than 50 degrees C or 122 degrees F that the thermo valve leaks.
3. Allow the engine to warm up until the coolant temperature exceeds 80 degrees C or 176 degrees F and verify that the thermo valve will hold a vacuum.
Note: If the thermo valve fails and must be replaced use 3M locking sealant 4171 or equivalent and torque the thermo valve to 20 to 40 Nm (15-30 ft. lbs.). Do not use wrenches or pliers on the resin part of the valve during installation.
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When to See a Mechanic
Stop DIY work and contact a certified mechanic immediately if any of the following apply:
- β’ You smell fuel, burning insulation, or see smoke.
- β’ Brakes feel soft, pull hard to one side, or make grinding noises.
- β’ The engine overheats, stalls repeatedly, or misfires under load.
- β’ You are missing required tools, torque specs, or safe lifting equipment.
- β’ You are not confident in the next step or safety outcome.