Symptoms are as follows:

Car surges pretty bad when cold
Noticeably laggy throttle response
Gas mileage went from 24mpg to about 19

I have noted long term fuel trims as high as -7 percent at highway speeds while cruising in 5th gear. I watched the upstream 02 sensor as well, and notice that the waveform was hanging up around .68 Volt with little to no oscillation. I am not seeing a nice crisp square wave that I was expecting. Is this normal, or do I have a bigger issue?

The 02 waveform is also hanging high at times during idle, I will see it float around .7 for five seconds or so, and then dip just a tiny bit ( not even close to a full swing).

Is there a decisive test that I can perform to help me confirm that my 02 sensor is in fact taking a dump on me before I drop $300 on another sensor? Any thoughts?

 

Denso 234-4741 Oxygen Sensor is a direct fit OEM replacement that is much cheaper at rockauto for $38 or $50 at amazon if you decide not to go through the dealership.

 

Really? No reliablility issues with that part? Sounds too good to be true!

 

Alright so today on my lunch break, I observed a waveform that was legit stuck high at .76 volts, for an extended period of time. The waveforms sometimes resemble square waves but often look more like a staircase, I am fairly sure this sensor is shot.