98 Civic CX Oxygen Sensor

Okay.

Like you, I am seeing a huge variation in price for my 1991 Civic's oxygen
sensor. My car has only a single sensor.

snip

Hm... I thought the main purpose of the rear oxygen sensor (downstream of the
catalytic converter) was to monitor the operation of the catalytic converter. I
see on the net that it also may (or always) input some information to the
computer (with the front oxygen sensor) to regulate the fuel/air ratio; to
fine-tune it.

Based on this and some other experience, I'm doubtful that failure of one oxygen
sensor leads to failure or even significantly more strain on the other.

Thanks for the info.

My 1991 Civic is pre-OBD (onboard diagnostics) II and uses only one oxygen
sensor. Its maintenance schedule does not even mention the oxygen sensor.

Yet online I am seeing recommendations to make it part of preventive
maintenance. E.g. http://www.volksparts.com/o2sensors.htm , about 2/3rds down,
in red.

Based on this discussion and seeing others with 1991 Civics have replaced
theirs, I think I'll replace mine (the original, now 13+ years and 152k+ miles
old) within the next couple of months.

I hope your repair goes well and your car is back on the road soon.

Mike -- I see I misread your comment about O2 sensors and the Federal/California
warranty. We both agree they are covered for a certain period. I guess what's at
issue is how long this period is.

 

non heated too? and cheaper, likely.

yeah. it lets the computer compare "before and after" notes to adjust the
fuel mix. possibly also to monitor how the cat is doing as well.

ya never know. one reason i got my O2 so soon after it failed aside from the
glowing orange light was i didnt want to possibly get thecat too hot, foul
it, or foul the downstream sensor. i dont know whether its designed to lean
out or richen the mix when it flags an error code. i *do* know that the car
had a lousy low speed idle when the CEL was on, and even stalled a few times
when i was coming to a stop. completely abnormal for the car until then, and
it hasnt happened since i replaced it.

are you getting bout the same mileage as when you got the car?

well, im not one to look a gift horse (or free sensor) in the mouth, and
checked it out here and in my warranty manual. the following parts on the
civic are covered by the 7/70 warranty, which would have applied to me (45k
miles)-

engine control module
transmission control module
powertrain control module
throttle body
intake manifold.

 

I see it is single wire and therefore unheated, yes.

The lowest price I've seen for my 1991 Civic's O2 sensor is $32 for an OEM
Walker. The highest price online is around $150. So, yes, this range beats the
range we have seen so far for the 1998 Civic, and yes, as you know, the 1998
Civic should have a heated O2 sensor.

No, definitely to monitor the catalytic converter by comparing the "before cat
conv" (front sensor) and "after cat conv" (rear sensor) signals. I googled. See
for example http://www.boschusa.com/AutoParts/FAQs/OxygenSensors/ .

But other sites talk about an additional function: Fine-tuning the fuel/air
mixture and so supplementing after a fashion the front sensor's signal. I expect
there's some variation on this from one car model to another.

I'm not sure you're treating above the effect of, say, a failed front O2 sensor
on a so far correctly operating rear O2 sensor.

I certainly agree a failing front O2 sensor will affect car performance and may
reduce the life expectancy of the catalytic converter.

But I am doubtful a failed front O2 sensor will destroy the rear O2 sensor. From
my reading and understanding, the car typically runs rich with a failed front O2
sensor. This may harm the catalytic converter, depending. But how is this
harmful to the rear O2 sensor?

As I imagine you are aware, mileage improves somewhat over time after purchase
of a new car (as it breaks in), and then it can worsen due to failing
components.

In the last year, I have been getting the best mileage I have ever gotten: For
Spring through Fall, typically 42 mpg (and sometimes better). This is mostly for
suburban driving where there are frequent half mile stretches of 40 mph or so
where I live.

As I've posted here before, maintaining my 1991 Civic's PCV valve has made a big
difference. Had I started maintaining it before last year, I think that 42 mpg
or so would have begun occuring some years ago.

snip

You're right: The owner's warranty manual is the place to look.

For my non-California 1991 Civic, the warranty on the 02 sensor was 5 yrs/50k
miles.

 

Ok, guys, here is the final result of my little odissey:

1) Checked the part number at www.slhonda.com. Price there was
$159.38 (it is a dealer...)
2) Bought the part from www.prostreetonline.com for $88 plus taxes
(shipping was free). It turned out to be Denso part, which fit perfectly
3) An informal mechanic friend installed it for me. It was very easy and
the sensor is located in the easiest possible part of the motor. Paid
him well worth $30.

Total spent: $88 + $7 (taxes) + $30 = $125
Original dealer price: $345.
Savings: $220.
Result: Cooooool!

Thank you all for your inputs. This newsgroup is awesome!
-H

 

Aside: I have been trying to determine who makes the Honda OEM oxygen sensors.
My local dealer said simply, "Honda." (*&^%$) Majestic (a popular online parts
site) said, "It's OEM. That's all we know."

I took out my oxygen sensor the other day to see if there were any incriminating
marks. Stamped on the side was what looked like the letters "ND." They had a
circle around them. The right side of the N and left side of the D were one in
the same. I am guessing this stands for NipponDenso (now just "Denso"). Also,
one internet site said something about Denso making Honda's oxygen sensors.

Can anyone confirm the OEM part is a Denso part?

2nd aside: Autozone in my area does loan out the special oxygen sensor socket
for a fully-refundable deposit. This and a few soaks with PB Blaster made
removal a piece of cake on my 91 Civic.

Thanks for the update, Hermes.

 

sensors.

correct! bothe my old on and the one i replaced are both denso. thats on a
98 civic, but denso has been around for a long, long time.

ND is denso, like ND spark plugs.

 

Excellent. Thanks.