Air/Fuel Mixture: Adjustments

Apply parking brake and do not accelerate engine. Place manual transmission in neutral; automatic in drive.
1. Start engine and allow to reach normal operating temperature, then turn engine off.
2. Turn each mixture screw to its full rich position. Note position of screw head slot inside limiter cap.
3. Carefully remove each limiter cap by installing a sheet metal screw in center of cap and turning clockwise. A soldering gun may also be used to cut through plastic caps.
4. Reset idle mixture screw(s) to approximate position noted before removing the limiter cap(s).
5. Connect tachometer and start engine. Apply parking brake and block drive wheels. Place manual transmission in neutral; automatic in drive.
6. Adjust curb idle speed to specifications.
7. With each mixture screw at its full rich position as established in step 4, turn each screw evenly towards the leaner position (clockwise) until a definite loss of RPM is noted.
8. Turn each mixture screw evenly in the richer direction (counterclockwise) until the highest RPM is obtained. Do not turn screws any further than point at which highest RPM is noted. This is the lean best idle position. Engine speed will increase above the curb idle speed an amount that corresponds approximately to the lean drop specification to be referred to in the following step.
9. Turn each idle mixture screw clockwise in small equal amounts until the following idle drop RPM specifications are obtained: V8 with automatic transmission, 20 RPM; except. V8 with automatic transmission, 50 RPM. If the final RPM differs more than 30 RPM from the originally adjusted speed, adjust curb idle RPM to specifications according to step 6 and repeat steps 8 and 9.
10. Install blue replacement idle limiter cap(s) onto mixture screw(s) with limiter tab positioned against the full rich stop position. Use care to avoid disturbing adjustment.