New O2 Sensor, Fantastic Mileage, then down the shitter again

[Anto]

I recently installed a new OEM fit Denso oxygen sensor.
I pulled out my old one & discovered that the ceramic element had shattered and the car was running very rich.
Previously, I got 20-23 MPG, and since the install of the new o2 sensor, my MPG shot up to 28.

It stayed like that for about 300 miles, then went back down again. My driving habit has not changed since the new sensor.
WHAT THE HELL.


Any ideas?

[bigOdom1]

change it again to see if it is broken/fouled

[g6civcx]

Pull the oxygen sensor and check. Your motor may be fouling the sensor.

[kingkilburn]

Shouldn't he look into what may have caused the change before replacing the sensor again?
Just a thought.

[98koukile]

28mpg for one tank of gas could be the difference between more highway less city... but you may want to borrow a wideband to check AFR

[98s14inaz]

Shouldn't he look into what may have caused the change before replacing the sensor again?
Just a thought.

Yes. A bad o2 sensor could be a sign something is bad with the tuning...or just an old o2 sensor. Either way, give the car a tune up and check the o2 sensor.

[-rip it up s13-]

thats weird cuz mine keeps doing that!!!!!!! i have stock injectors and fuel pressure, i put on a t28 and turned up the boost to 9 p.s.i and my o2 keeps fouling out and it ends up running really rich and back firing!!

[98s14inaz]

thats weird cuz mine keeps doing that!!!!!!! i have stock injectors and fuel pressure, i put on a t28 and turned up the boost to 9 p.s.i and my o2 keeps fouling out and it ends up running really rich and back firing!!

What are you using for tuning?

[gotta240]

TUNING??? WHATS THAT?!?!?! lol... wait for it, wait for it

[98s14inaz]

TUNING??? WHATS THAT?!?!?! lol... wait for it, wait for it

If you say safc I'm going to have sex with your skull...lol