5.9L V8
- Remove carburetor. Remove idle mixture screw tamper resistant caps. Install carburetor. Bring engine to normal operating temperature. With engine running and transmission in neutral, adjust curb idle to 600 RPM.
- Turn mixture screws clockwise (leaner) until engine speed begins to drop. Then turn screws counterclockwise (richer) until highest RPM reading is obtained for best lean idle. Turn screws clockwise until specified lean drop RPM is obtained (20 RPM).NOTE: If final RPM differs more than 30 RPM from specified curb idle, reset curb idle and repeat mixture adjustment.
- Carefully install new mixture screw tamper resistant caps. DO NOT move mixture control while installing caps.
NOTE:
On vehicles with fuel injection, air/fuel mixture is controlled by Electronic Control Module (ECM) and is not adjustable. On carbureted models, adjust air/fuel mixture only when vehicle fails emission test or carburetor is disassembled.
IDLE SPEED
| Application | Idle RPM | |
|---|---|---|
| 2.5L, 4.0L & 4.2L | ||
| 50 States | 680 | |
| High Altitude | 700 | |
| 5.9L | 600 | |