First is all always write down the codes you have present, it helps in closing down on the problem. I am assuming you have a 95 Mazda Milleinia
1. Start and run the engine and monitor the oxygen sensor signals and see if this sensor has bad readings still. Check for an open or shorted wire between the sensor and the Engine Control Module (ECM) if the signal is dropping out.
2. Listen for an exhaust leak in the area of the oxygen sensor, the leak could allow oxygen in to the exhaust and skew the sensor readings.
3. Inspect the ECM and ECM connector for signs of something that has been spilled on the ECM.
Is the engine idling too high or too low then check this:-
1. Unplug the idle air control valve and turn the air bypass screw in to see if it will idle down. If it will idle down, adjust the idle speed to around 500 RPM's and then plug the idle air control valve back in.
2. If it still idles high, remove the air boot from the throttle body, block the air bypass ports with duct tape, hook the air boot back on and start it. This should make it not idle at all or just barley idle. If it does, the problem is in the idle air control valve.
3. If blocking the air ports doesn't cause it to idle down, the throttle plate must be sticking open. Clean the throttle plate really good and back the throttle stop screw off and then see if it idles down.
4. Verify the coolant level is not low and that coolant is circulating through the idle air control valve.
Tech Tips:
This idle air control valve is two valves in one. It is a fast idle thermo valve on one side and a duty cycle idle air control valve on the other.
I’m happy to assist further over the phone at
https://www.6ya.com/expert/uttamjeet_2f3adc18600f8ede
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