Air/Fuel Mixture: Adjustments

1. Warm engine to normal operating temperature and adjust timing. Remove cover from diagnostic plug (on fender panel near hood hinge). Connect voltmeter negative lead to pin 3 of plug, and positive lead to battery positive.
2. Disconnect oxygen sensor plug (near sensor under vehicle). Observe voltmeter reading and place a piece of tape on voltmeter dial to indicate needle position. The needle should not be moving.
3. Reconnect oxygen sensor. The needle should vibrate and the vibrations should be centered around mark on the voltmeter. If not, then adjustment is necessary.
4. Remove the plug from the mixture control unit (between the fuel distributor and the air flow sensor funnel), by removing the two shear bolts that hold the plug in place. To remove the shear bolts:
a. Use the appropriate size drill and screw extractor, or
b. Use a large drill and drill just the head off of the bolts.
Be very careful to ensure that no metal chips get into the engine.
5. Insert a long 3mm Allen wrench and adjust air/fuel mixture screw until needle is centered around mark on voltmeter dial. Remove test equipment and plug the adjustment opening.