O2 Sensor - Non-Chevy Question

[Zilverado]

Please forgive me for asking this question regarding my wife's daily driver ('92 Pathfinder)...

The engine runs well when cold. Once it reaches operating temp (about 5 to 10 min. driving), it starts to miss, and hesitate - almost stall. This goes on for a couple of minutes and then all is well. This happens every day, but only the one time, and then it's good.

I've had it suggested that it could be the O2 sensor. Do these cause such intermitent trouble? Is there any way of testing these?

Extremely grateful for any advice.

[Mike76251]

It could very well be.
When cold, the engine probably doesn't use the 02 sensor because it has to heat up to work and the computer knows that.

When the engine heats up and heats up the 02 sensor......the computer turns on the incoming signal from that sensor and sees that it cannot read it so it goes into "limp-home" mode.

I know I will get slammed for that logic trail because it is supposed to have a heated sensor but Nissan's computers don't work like GMs do and if I remember right they ignore the 02 sensor till it heats it and instead uses a program mode.

[Zilverado]

Since I know nothing about O2 sensors, I'll ask another silly question:

Does this mean that, if I disconnect the O2 sensor and get the same performance, that could be the problem? Or would disconnecting the sensor screw up the computer?

[Mike76251]

That's not a silly question!
I would try that when it goes through all the cycles you described and is at the state you describe as "all is well".
If it doesn't change anything by unhooking it then it is definitely bad.

[phantom dually]

Have the cats checked? They may be clogged.

[Zilverado]

Originally posted by Mike76251
That's not a silly question!
I would try that when it goes through all the cycles you described and is at the state you describe as "all is well".
If it doesn't change anything by unhooking it then it is definitely bad.

So I should not disconnect it until after it has run the cycle, and is running smooth again? Not before? What would I notice if I unhook a properly functioning sensor - just rough idling, or what? And where would I typically find the plug to unhook it?

Also Phantom - how do I "check" the cat? I assume it would need to come off for this?

Thanks,

[Zilverado]

So I took the car out for a ride this morning, waited till the problem came and went. Disconnected the O2 sensor (found the connector under the hood) and nothing changed. The idle stayed smooth. Drove all the way home with it disconnected - no problem. I think I may have found it.

I'm going to leave it disconnected for now and see what happens.

Any further advice? Should I replace this myselt or does a shop need to do some computer magic on it?

[phantom dually]

Replace it yourself. Easy to do. They have a socket that you can take it out with that ismade for the 02 sensors wires to go around. You can rent one at most stores.