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 MANUALSSUBARU1991LOYALE 4D SEDAN, 1.8 5, STANDARDREPAIR AND DIAGNOSISENGINE PERFORMANCESYSTEMENGINE CONTROLS - SYSTEM/COMPONENT TESTSTURBOCHARGER COMPONENT TESTINGBOOST PRESSURE TESTING
1991 Subaru Loyale 4D Sedan, 1.8 5, Standard
Boost Pressure Testing
1991 Subaru Loyale 4D Sedan, 1.8 5, StandardSECTION Boost Pressure Testing
- Disconnect wastegate duty solenoid connector. Engine must be at normal operating temperature. Disconnect rubber hose from pressure switch. Using a "T" fitting, connect an air pressure gauge. Use enough hose so that gauge may be carried inside passenger compartment.
- Boost pressure should be checked at 2400 RPM with a wide open throttle. Normal pressure is 14.5-17 in Hg. (7.3-8.3 psi). Reconnect wastegate duty solenoid.
- If boost pressure is too high, check the rubber hose that connects the intake manifold to the wastegate valve. Replace if defective. If wastegate valve is not operating and remains closed, replace the turbocharger. If boost pressure is too low, replace the turbocharger.
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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.