95 Pathfinder, Trouble Code 33, O2 Sensor

[friedk]

Can anyone assist me

 

I have a 5Spd 95 Pathfinder that I use for camping trips in the summer. I noticed that last year when loaded down with my 2 kayaks on top that the check engine light comes on pretty quickly especially on secondary roads. Soon the engine will sporadically begin to lag, almost stutter while my

foot is on the accelerator. It will come out of this rough period only when I really give it quite a bit of gas. When nothing is in the truck and I am taking it to do my errands none of this happens. Distance, Weather etc does not seem to matter. The only thing that I seem to note is that it will not do it as easily on the highway. So it seems to occur more on secondary roads.

 

The engine does not apear to be overhead but this occurs when the engine is at running temperature usually traveling at lower speeds. During these periods that the check engine light is on it does not run rough constantly. After I unload everything the error code clears and it seems to run normally.

 

The computer gives me error code 33 - the o2 Sensor

 

I am not sure if I can self test the 02 Sensor by pulling it out and see if it runs better because it only runs rough as explained above. Should I just replace the sensor and see how it does on my next trip?

 

The one thing that seemed to start this is I had an exhaust leak at the top of the Y pipe on the Pass Side last year that on one trip it really heated up the fire wall and that was the first time the check engine light came on. I have since replaced that section of the Y hopeing it would cure the problem. But it has only fixed part of the problem.

 

Thanks for your imput.

[k9sar]

diagnostic procedure 30 in the 95 FSM suppliment will walk you through the check of the O2 circuit and sensor

 

if you want a quick check... disconnect the O2 sensor and check the resistance between the outermost terminals. It should be between 1 and 1000 ohms. The rest of the procedure checks the circuit from the ECU etc.

 

From your description however, it sounds like a bad connection. While checking the resistance on the O2 sensor, have someone reach under and fiddle with the wire to see if you have a break in it. If so, teh resistance will not hold constant and will temporarily 'open'. The ECU used the O2 sensor to determine the mixture (and other things) and will adjust it when not needed and your truck will get crappy mileage and run like sh!t.

Edited May 19, 2009 by k9sar

[friedk]

Might I be able to replicate the problem by running the engine and wiggling the wire from the top to see if this affects the idle? If it was a wire why do you think the problem would only occur when the truck is loaded with gear and on secondary roads? Before reading the code I thought it might be more of a heat issue. But the engine does not seem to be overheating.

[94extreme]

yeah, check the connection first otherwise it is the 02.. they tend to act up for a while before they completely expire.

[friedk]

Ok,

 

I just dont want to miss something else that could be the problem. Because it occurs only when the truck is loaded and the engine heats up on secondary roads. I suppose that the O2 sensor could be weak and heating it up is enough to cause it to malfunction.

 

I am finding exact fit O2 sensors from $85 (Autozone) to $105 (NAPA)

[k9sar]

The wire for the O2 sensor lays over your tranny on it's way up to the passenger side connection point. Perhaps a hott tranny is affecting it.

 

When I read "secondary roads", I was thinking bumpier than normal, thus bouncing/flexing of the wire, especially if you have a broken exhaust mount or something.

 

My o2 was from advanceauto, it was a Bosch, universal fit with a snazzy universal connector to splice the new sensor to your old connector. It was a bit cheaper than the Bosch one with the OEM conenctor.

Edited May 19, 2009 by k9sar

[friedk]

I took it for a short trip today and got the engine up to running temp. No error code, things seemed to run just fine as usual when not loaded on a trip. I unplugged to O2 sensor and nothing seemed to change at all. I do notice an odd smell at the exhaust, not like rotten eggs but a strong odor. During my test the check engine light did not come on. Seems that this is related to the O2 sensor or wire which seems in tact.

 

Any thoughts about a plugged cat?

[k9sar]

Any thoughts about a plugged cat?

 

yea... feed it lots of fiber and keep the litter box clean so it doesn't crap on the floor

[friedk]

I will keep that under my hat for consideration... Thanks

 

 

How do I determine if my problems is the O2 sensor vs a bad catalytic converter. Could the catalytic converter create back pressure only when the engine is warm and under a load... or if the catalytic converter was bad wouldnt it give me problems constantly? I hate to replace one and find out it is the other.

 

Sorry guys I am not much of a mechanic but always learning so thanks for your help.