Adjustment of turns of idling and quality of a mix

Electromagnetic idle speed control

Air flow meter

The idle speed is set by the EEC IV module only and manual adjustment is not possible.

Engines with catalytic converter

On engines with a catalyst, the mixture quality is controlled by the EEC IV module and manual adjustment is not possible.

Engines without a catalyst

Seal of the screw for adjusting the quality of the mixture

The screw seal is indicated by an arrow.


Air flow meter upside down.

Mix quality adjustments

Before adjusting the quality of the mixture, you must:

• check and, if necessary, adjust the valve clearances;
• check the condition and, if necessary, replace the air filter;
• check the condition of the ignition system;
• warm up the engine to operating temperature.

1. Connect a tachometer to the engine (with the ignition off) and gas analyzer.

2. Increase the engine speed to 3000 rpm and hold it for 15 seconds, and then turn the engine to idle.

3. Take instrument readings.

4. If the CO content deviates, remove the protective cap from the mixture quality screw, increase the engine speed to 3000 rpm and hold it for 30 seconds, and then switch the engine to idle mode and, turning the screw, set the required CO level.

5. On DOHC engines without a catalyst, remove the cap from the mixture adjustment potentiometer (located on the right in the engine compartment, behind the total pressure sensor) and turn the screw to obtain the desired CO concentration. If the adjustment does not give a change in the readings of the device, it is possible that the potentiometer is in the extreme position. To set it to the center position, turn the adjustment screw 20 turns clockwise and then 10 turns counterclockwise and repeat the adjustment.


6. On V6 engines, the front air flow meter must be adjusted first. Adjustment of the rear airflow meter should only be done if the adjustment range of the front one is insufficient.

7. Turn the mixture adjustment screw with a hex wrench until the desired CO level is reached.

8. Turn off the engine and disconnect the gauges.