96 Maxima O2 problem?

I have a 96 Max with over 285k miles. I have never really had many
issues with it beyond the usual maintenance and wear and tear.
However, for the last 3 years, almost all of my emission sensors have
been replaced. I thought I was through with all that for another 200k
when my "Check Engine" light just recently came back on. It was 0503,
the RH Heated O2 Sensor.

I purchased the normally $80 part online for about $50. It was an SNG
sensor. I replaced it, reset the computer and drove. I also replaced
my fuel filter and added a short-ram intake kit all on the same day.
Almost a week later, the light came back on. It was the same code. I
cleared it, and it came back on the within miles.

I have reset it a few times. Since all of this, my car has been
getting less MPG, from about 27MPG to 18. Moreover, it has now
started to hesitate when I am accelerating from a stop or from less
than 20mph. It is almost acting as if it is not getting gas or
something.

It drives fine on at highway speeds. It accelerates a little faster
to 60, 70, 80 and so on. In addition, I have been able to drive at
80, 90 and even 100 without the car going over 3,000RPM. I attribute
that to the air filter mod, but I could be wrong.

Therefore, Nissan community, what do you think the problem is? Is my
new O2 sensor bad? If I had bought it locally, would you have
suggested I returned it already? On the other hand, is it the mod or
something else?

* I will let you all know that I am no expert but I have done most of
the work on my car (CV axle replacement, radiator and such), so I am
no slouch. However, I am lost on what I should do next.

On Mar 6, 9:02 pm, "Charlie 3" <Just... RemoveThis @gmail.com> wrote:
> I have a 96 Max with over 285k miles. I have never really had many
> issues with it beyond the usual maintenance and wear and tear.
> However, for the last 3 years, almost all of my emission sensors have
> been replaced. I thought I was through with all that for another 200k
> when my "Check Engine" light just recently came back on. It was 0503,
> the RH Heated O2 Sensor.
>
> I purchased the normally $80 part online for about $50. It was an SNG
> sensor. I replaced it, reset the computer and drove. I also replaced
> my fuel filter and added a short-ram intake kit all on the same day.
> Almost a week later, the light came back on. It was the same code. I
> cleared it, and it came back on the within miles.
>
> I have reset it a few times. Since all of this, my car has been
> getting less MPG, from about 27MPG to 18. Moreover, it has now
> started to hesitate when I am accelerating from a stop or from less
> than 20mph. It is almost acting as if it is not getting gas or
> something.
>
> It drives fine on at highway speeds. It accelerates a little faster
> to 60, 70, 80 and so on. In addition, I have been able to drive at
> 80, 90 and even 100 without the car going over 3,000RPM. I attribute
> that to the air filter mod, but I could be wrong.
>
> Therefore, Nissan community, what do you think the problem is? Is my
> new O2 sensor bad? If I had bought it locally, would you have
> suggested I returned it already? On the other hand, is it the mod or
> something else?
>
> * I will let you all know that I am no expert but I have done most of
> the work on my car (CV axle replacement, radiator and such), so I am
> no slouch. However, I am lost on what I should do next.

Have you changed the coolant temp sensor? When that sensor goes bad
you never see a code. The car's milegae gets worse and power gets a
bit weaker. Before you replace the O2, I would try that.

Also, once changed, the ECU needs 2 or 3 tankfuls to relearn its feul
curve according to the readings that its now getting from the replaced
temp sensor.

CD