Emission Control Systems: Adjustments

Fig. 5 Idle Speed Adjusting Screw:

At elevations above 8200 ft. with the barometric pressure below 550mm Hg, do not adjust idle speed as this may cause improper operation of the ISC solenoid valve.
1. Ensure ignition timing and valve lash are properly adjusted, all vacuum hoses and engine harness connectors are securely connected, the air cleaner is in good condition, accelerator cable is properly adjusted, and all accessories are off.
2. Connect suitable tachometer to engine following manufacturer's instructions.
3. On vehicles equipped with manual transmission, place gear select lever in neutral.
4. On vehicles equipped with automatic transmission, place gear select lever in park.
5. On all vehicles, block drive wheels and apply parking brake.
6. Start engine and run until it reaches normal operating temperature.
7. Open throttle until engine speed exceeds 1500 RPM, then allow engine to return to idle speed slowly.
8. Ensure idle speed is within specifications, refer to ``Tune Up Specifications.'' Adjust idle by turning idle speed adjusting screw, Fig. 5.