1988 Pontiac Fiero Base, AutomaticFACTORY OEM SERVICE PROCEDURE

Est Performance Check

  1. The ECM will set timing at a specified value when diagnostic test terminal of the ALDL connector is grounded. To check the EST operation, perform the following steps:
  2. Start and run engine at 1500 RPM with the ALDL diagnostic test terminal NOT grounded. Ground test terminal. When ALDL test terminal is grounded, there should be a noticeable change in engine RPM. When a fault in the EST system takes place, a code 42 should be set.
  3. If a code 42 is set, use appropriate chart for diagnosis. If symptom is engine miss and the direct ignition system is suspected, use CHART C-4D DIS MISFIRE for proper diagnosis. See appropriate TESTS W/ CODES article article in the ENGINE PERFORMANCE section for testing and diagnosis information. Refer to the following list.
Fig 1: 2.8L Direct Ignition System Components
G7834
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:

  • • 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.

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