1988 Chevrolet Hi-Cube 5.7 M, 475/M40FACTORY OEM SERVICE PROCEDURE

Est System: Notes

The ECM monitors information concerning crankshaft position, engine RPM, engine load, atmospheric conditions, engine temperature, and transmission gear position. This information is used by the ECM to compute desired spark timing which is relayed to the distributor, enabling appropriate changes to be made to ignition timing. A back-up spark advance system is incorporated to signal ignition module in the event of ECM failure.

CAUTION: Although similar in appearance, components of HEI/EST and HEI distributors are NOT interchangeable.
Factory Service Tools

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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.

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