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 DIAGNOSISENGINE PERFORMANCEIGNITION SYSTEMIGNITION SYSTEM - HEI (CARBURETED MODELS)SYSTEM TESTINGINTERMITTENT SYSTEM PROBLEMS
1987 Chevrolet Forward Control 4.8 T, Automatic, 400/M40
Intermittent System Problems
1987 Chevrolet Forward Control 4.8 T, Automatic, 400/M40SECTION Intermittent System Problems
- Check spark at 2 plug wires using test plug. If no spark occurs, refer to ENGINE WILL NOT START section. If spark occurs from one or both spark plug wires, check pick-up coil with ohmmeter. Refer to PICK-UP COIL in COMPONENT TESTING section in this article.
- Replace pick-up coil if defective. If unit tests good, check for dwell increase from high to low RPM. If dwell did not increase, replace electronic module. If dwell did increase, and trouble is not found, check fuel, coil and plug wires, and cap and plugs.
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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.