Bad O2 sensor

[matt8urton]

Can anyone give my the symptoms of a bad O2 sensor? When I am idling or low RPM and step on it, the engine sputters a bit. My gas milage seems to suck too.
Also I've seen sensors that cost $30 and ones that are $150, any opinion on the quality?
Thanks

[smj999smj]

O2 sensors can fail in a number of ways so symptoms can vary. It can cause an engine to run too lean or can cause it to run too rich. Sputtering, excessive gas consumption, fouling spark plugs are all signs of an engine running too rich. Surging, pinging under load, blistered spark plugs, misfiring are all signs of an engine running too lean. The O2 sensor is the ECM's main input for determining how much fuel to inject into the engine. They do tend to lose efficiency over time; if you have a WD21 Pathy with its original O2 sensor, you've certainly gotten your money's worth out of it and should replace it just for sake of routine maintenance. There is a procedure to test the sensor using an ohmmeter in the FSM.

As far as replacement sensors, yes, there is a wide range of choices. As far as the sensor, itself, most of them are pretty similar. The biggest differance is in fitment and their choice of element in the sensor. There are two main types of sensors: universal fit and direct fit. Universal fit sensors use the harness and connector of your old sensor while direct fits are made to plug and play, so to speak. Thus, universal fit sensors are a lot cheaper, but can be prone to problems if the terminals in the original connectors are weak or worn or the splice connections fail. For those reasons, I recommend spending a little more and getting a direct fit sensor. As far as brands, NTK (a division of NGK) and Bosch are both OEM suppliers of O2 sensors to Nissan. Denso is an OEM supplier to Toyota. I have no problem with any of those brands. You can usually get O2 sensors at a good price at Rockauto.com. Now, whether replacing the O2 sensor will fix your problem, I cannot say. I would recommend checking the fuel pressure with a gauge and seeing if it's within spec (you may have a bad regulator causing high fuel pressure). Also, make sure it's not due for a tune-up; if you repace any ignition componants, stick with genuine Nissan or NGK brand parts.

[matt8urton]

Thanks alot for the info!

[matt8urton]

Sorry I'mreally new to this but what does FSM and ECM stand for?

[mar1]

FSM factory service manual

ECM/ECU is engine control module/unit

[matt8urton]

Any advice on how to disconnect the O2 wiring, small space and I have no idea where it leads to?

[ajt]

hey guys,

I just got an 88 pathfinder. pulled plugs and it appears to run rich, I saw this thread about 02 sensors.

I was under the impression there were multiple 02 sensors, are you guys talking about one in particular that would be the culprit to this problem.

the pathfinder i have bogs down, when i hit the gas.

[smj999smj]

WD21 Pathfinders only had one O2 sensor.

[ajt]

ok good to know.... much cheaper to replace one.

can you clean them up or better to just replace

[smj999smj]

If it has a lot of miles on it or tests bad, replace it.

[noe58]

check the cam sensor also had a similar problem if your truck runs good when it's cold then after it warms up runs like crap with the gas mileage of a hum v no power stuttering and just plaincrappy