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Home >> Buick >> 1988 >> Skyhawk S/E, Automatic >> Repair and Diagnosis >> Engine Performance >> Ignition System - Direct >> Testing >> Est Performance Check

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-1 DIS MISFIRE AT IDLE or CHART C-4D-1 DIS MISFIRE UNDER LOAD in the 2.0L VIN [1] TBI CEC TESTS W/CODES article in the ENGINE PERFORMANCE section for proper diagnosis.
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