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Home >> GMC >> 1990 >> Forward Control 6.2 J, Standard >> Repair and Diagnosis >> Engine Performance >> Engine Controls - Adjustments >> 4-Cylinder Ignition Timing >> Engine Controls - Adjustments >> 2.5L (VIN E)
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2.5L (VIN E)

  1. Set parking brake, block drive wheels and place transmission in Neutral or Park. Warm engine to normal operating temperature. Turn A/C off (if equipped). Ensure SERVICE ENGINE SOON light is off.
  2. Ground terminals "A" and "B" at ALDL connector. SERVICE ENGINE SOON light should begin flashing. Connect timing light.
  3. Set average timing of cylinders No. 1 and No. 4 to specification and adjust if necessary. See 4-CYLINDER IGNITION TIMING SPECIFICATIONS  table. Remove jumper from ALDL connector. Ensure SERVICE ENGINE SOON light is off.
4-CYLINDER IGNITION TIMING SPECIFICATIONS (Degrees BTDC @ RPM)

Application Man. Trans. Auto. Trans.
2.5L (VIN E) 8 @ Idle 8 @ Idle
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