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 MANUALSCHEVROLET1987V 30 P/U 4WD V6-262 4.3LREPAIR AND DIAGNOSISPOWERTRAIN MANAGEMENTCOMPUTERS AND CONTROL SYSTEMSENGINE CONTROL MODULEDESCRIPTION AND OPERATIONMODES OF OPERATIONELECTRONIC SPARK TIMING (EST)
1987 Chevrolet V 30 P/U 4WD V6-262 4.3L
Electronic Spark Timing (EST)
1987 Chevrolet V 30 P/U 4WD V6-262 4.3LSECTION Electronic Spark Timing (EST)
The Electronic Spark Timing (EST) distributor contains no vacuum or centrifugal advance mechanisms. In addition to the connectors normally found on HEI distributors, the HEI-EST distributor also has four wires going to a four terminal connector. A reference pulse, indicating engine RPM and crankshaft position is sent to the ECM. The ECM determines the proper spark advance for the engine operating conditions and sends an "EST" pulse to the distributor.
In the case of EST failure, a back-up spark advance system is incorporated in the module.
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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.