O2 Sensor tip.

[Steve40th]

I went to change the O2 sensor in my 02 Corolla, and when I went to loosen it, it was already loose. So, I snugged it back to where I thought it was, as I only started on one nut. Well, I then started the car, and there was a puff of continuous air coming out around where the gasket is.
Well, I took out the old sensor, 100,000 miles, and put in the new one. Car runs better, no pinging at light throttle during shifting, and it idles lower than what it did before.
So, maybe it would be good to check tightness of your O2 sensor.
I did the one prior to the cat.

[ilovecorollale]

So your saying to make sure its not loose or does the tightness of it affects the idle and mpg because i changed mine recently and everything seems well but my mpg went even lower than before.

[Steve40th]

Originally Posted by ilovecorollale

So your saying to make sure its not loose or does the tightness of it affects the idle and mpg because i changed mine recently and everything seems well but my mpg went even lower than before.

Yes, verify it is tight. Mine was loose and had an exhaust leak at the sensor because it was loose. This affects air fuel ratio. Now that it is tight, and a new sensor, the car runs much smoother. No more light pinging between shifting gears.