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 MANUALSCHEVROLET1987FORWARD CONTROL 4.8 T, AUTOMATIC, 400/M40REPAIR AND DIAGNOSIS (SINGLE PAGE)ENGINE PERFORMANCESYSTEMRESTRICTED EXHAUST SYSTEM CHECK (CHART B1)TROUBLE SHOOTINGCHART B1 - RESTRICTED EXHAUST SYSTEM CHECKS
1987 Chevrolet Forward Control 4.8 T, Automatic, 400/M40
Chart B1 - Restricted Exhaust System Checks
1987 Chevrolet Forward Control 4.8 T, Automatic, 400/M40SECTION Chart B1 - Restricted Exhaust System Checks
NOTE:
Proper diagnosis of restricted exhaust system is essential before any components are replaced.
- Remove the rubber hose from the exhaust manifold AIR pipe check valve.
- Connect fuel pump pressure gauge to hose and nipple from Propane Enrichment Device (J26911).
- Insert nipple into exhaust manifold AIR pipe.
- With engine at normal operating temperature and running at 2500 RPM, observe exhaust system backpressure on gauge.
- If backpressure exceeds 2 3/4 psi, a restricted exhaust system is indicated.
- Inspect entire system for collapsed pipe, heat stress or possible internal muffler failure.
- If there is no obvious reasons for excessive backpressure, a restricted catalytic converter should be suspected and replaced.
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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.