Checking and adjusting the frequency and proportion of the idle mixture

1. Idle speed - the speed at which the engine rotates when the gas pedal is not pressed. This indicator is critical both for the operation of the engine as a whole and its subsystems.

2. When adjusting the idle speed, you must use a tachometer.

3. Before adjusting the idle speed, check the valve clearances and the ignition system (ignition timing, spark plugs) (see chapters 34, 35, 36 and 37).

4. Warm up the engine to operating temperature and make sure the choke is fully closed. Disconnect the cooling fan motor connector and turn off all electrical equipment and (if installed) air conditioner. On models with automatic transmission, set the lever to the position «N» and apply the parking brake.

5. Start the engine and compare the idle speed with the data given in the Specifications. If adjustment is necessary, turn the idle speed adjusting screw (photo).



6. To adjust the idle mixture ratio, an exhaust gas analyzer is needed (CO meter). If the gauge is not available, have the mixture adjusted by a Mazda dealer or other specialist.


7. Install an exhaust gas analyzer and run the engine to idle. Determine the CO content and compare it with the value given in Specifications. If adjustment is necessary, turn the mixture adjustment screw (photo).



8. If the mixture adjustment screw is covered with a plug, remove it to gain access to the screw.

9. When the idle mixture ratio is adjusted, recheck the idle speed and correct it if necessary.

10. Turn off the engine, disconnect the analyzer and connect the electrical equipment that was previously disconnected.