Air/Fuel Mixture: Adjustments

The mixture adjusting screw is recessed into the throttle body and sealed with a hardened concealment plug which prevents tampering during normal tune up procedures. If it is evident that idle mixture requires adjustment, remove plug as outlined in concealment plug removal procedure in ``FUEL SYSTEM''.
1. Disconnect electric cooling fan, if equipped, then ensure all lights and accessories are in ``Off'' position and transmission is in Neutral.
2. Start and run engine at fast idle speed until coolant is at normal operating temperature, then turn ignition ``Off.''
3. Disconnect battery ground cable for approximately 5 seconds, then reconnect it.
4. Disconnect exhaust oxygen sensor electrical connector.
5. Start and operate engine at 2,000 to 3,000 RPM for approximately 5 seconds, then allow engine to return to idle for 2 minutes.
6. Alternately adjust idle speed and idle mixture adjustment screws to obtain a CO reading in the .1-.3% range without causing engine to misfire.
7. Connect oxygen sensor, then adjust curb idle speed as previously described.
8. Fill concealment plug opening with a suitable sealant.