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4.2L 6-Cylinder

  1. Remove carburetor and locate roll pins blocking idle mixture screws. Drill through throttle body on closed end of roll pin hole. Drive pins out with punch. Install carburetor and connector tachometer.
  2. Bring engine to normal operating temperature and adjust curb idle speed to 680 RPM (50 states) or 700 RPM (high altitude). Place automatic transmission in Drive or Neutral for manual transmission. Turn mixture screws inward until RPM drops. Turn screws outward until highest RPM is reached.
  3. Turn mixture screws inward until RPM drops to 630 RPM (50 states) or 650 (high altitude). Adjust both screws equally. When mixture is correctly adjusted, replace roll pin to block adjustment screws.
NOTE: If final RPM differs more than 30 RPM from specified curb idle, reset curb idle and repeat mixture adjustment.
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