Why are my O2 sensors lasting so long?

I have 150k miles on my '99 Concorde with 2.7L engine. Fuel mileage has
been a pretty steady 25 to 28 mpg year round on my 80 mile daily
commute, and driveability is good. I always use mid-grade (89 octane)
name-brand fuel. I have never replaced my O2 sensors.

Is O2 sensor longevity helped by highway driving? Any other factors than
luck of the draw to explain why mine are apparantly still good.

Should I replace them pre-emptively, or in this case should I go with my
father's favorite expresion "If it ain't broke, don't fix it".

Based on previous reading, *if* I were to replace them, short of obvious
problems, I really only need to replace the upstream ones since the
downstream ones do not affect tuning (if what I have read is correct,
the downstream ones only determine whether a CEL gets lit to announce a
problem with the cats). Correct?

Is there a way to accurately assess their health (a voltage reading I
assume)? I ask this because (again from revious reading) they can drift
as they age and, though not bad enough to throw a code or cause obvious
running problems, might be causing inefficient tuning? IOW - is there a
wide voltage range for "barely acceptable" that mechanics use, and then
a tighter range to look for to mean not only acceptable, but "very
good/efficient"?

Bill Putney
(To reply by e-mail, replace the last letter of the alphabet in my
address with the letter 'x')

 

Yours probably AREN'T "still good"

An O2 sensor normal lifecycle is that as it ages, the speed that it reacts
gets
slower, it begins to get more 'lazy' This is visible on a scope and on
some
other diagnostic equipment long before the sensor actually stops working.

There's quite a lot of allowable variation in an engine control system. If
there
wasn't you would get CEL all the time as very minor exhaust leaks and such
that would normally be no problem would be setting it off.

That is a tough question in your case I think. If you have no obvious
drivability
issues, and your car still passes emissions inspection, and you would have
to
pay someone to do it, it would be very tough to justify.

I did my o2 sensor in my 95 T&C at 100K miles as purely a preventative
maintainence. There was no drivability change after doing it - but
according
to the average mileage on the ceiling mounted display, I'm now at around
14.5mpg instead of 13mpg. I think the sensor cost about $40, so it would
pay for itself in about 2,000 miles, since I did it myself in my driveway.

I'll pass on that question.

This is one of those things that I strongly suspect you have to do it and
see what happens. The one difference between an old out of range o2 and
a new on-spec o2 that a driver would see is mileage. If your mileage
measurements aren't that accurate it's possible that any change would be
lost in the measurement variance.

And even in my T&C, I have never checked the mileage the computer
is feeding me against reality, so I have no idea if I really did see a
1.5mpg
improvement.

Ted

 

If nothing else is wrong, it is not out of the ordinary for an O2
sensor to last 300,000 Km or more.

Listen to your dad. On a 99, you have OBD2 - and if the sensors get
lazy or otherwize malfunction, the car will tell you by turning on the
CEL and throwing a code.

You need a scan tool to see the voltage swing - a small or slow swing
means problems - but they WILL throw a code before they cause
driveability problems, in my experience.

 

You COULD assume the replacement will give you better fuel mileage,
but also remember the quality of replacement parts in the channel is
spotty - and what you put in MAY be worse than what you took out.
Infant mortality is too high, considering the price we are paying for
parts.

I have seen original O2 sensors still giving good strong crossovers at
well over 300,000Km and would not consider changing them as a
preventative measure in normal circumstances.

More O2 sensors get changed because of other causes than because of
failure. I had a "lean running" code on my wife's Mystique, and if I'd
have taken the advice of half the guys on the Ford list, I'd have
replaced all 4 very miserable to reach and quite pricy O2 sensors -
and still had the same problem, which ended up being a short rubber
hose that collapsed under high vacuum, and opened a crack when it
collapsed. Looked PERFECTLY normal when removed, untill you started
squeezing it. A $40 part from ford - not stocked by the dealer, and
replaced with about $2 worth of emmission hose.

 

Should I replace them pre-emptively, or in this case should I go with my

I had mine replaced on Isuzu Trooper, 136k miles. Although CEL was not lit,
I assumed sensors have lost their efficiency by now and replaced anyway.
It's hard to say if mpg has improved, but throttle response is definitely
better. I may have gained few HPs as well.

That's my understanding as well.

Be aware of el cheapo deals. General consensus is that Bosch O2 sensors are
crap, and probably wont last more than 10K

Peter

 

You should (at least the front ones); they're due. The deterioration in
O2S performance is usually very gradual, not catastrophic. There will
almost certainly be a noticeable improvement once you replace them, as
long as you don't do something dumb like using Bosch. Same goes for spark
plugs nowtimes. It used to be you could tell by sound and feel that the
plugs were getting old. Now it's common to replace very old plugs and find
them *grossly* worn out, and a common reaction is "Gee, I couldn't tell
from how the engine was running!"

Well...no, not really. The primary symptom of age isn't drift so much as a
loss of response speed, which is in the context of computer time, not
human-eye time. You can watch them switch with an analogue VOM, but you
can't tell if they're fast enough, a little slow, very lazy, etc.

DS

 

Mine lasted nearly 160K in my 96 minivan. I know many suggest
pre-emptively changing them like you do with spark plugs, but I don't
subscribe to that. The OBD system seems pretty good at catching a
failed O2 sensor, so I don't see a need to replace it pre-emptively
given the cost to do so.

Matt

 

Thanks for the great replies.

Sounds like there's no wrong or right decision in my case.

Reasons to replace: Possibly unnoticed but real degraded response and
slightly lower fuel mileage.

Reasons not to replace: Cost (not insignificant, not great, but
nevertheless a real cost) and (as validly pointed out by Mr.
Nospam.clare) a brand new aftermarket part may not be as good, accurate,
or long-lived as my 7 year old factory parts.

I probably will put it on my mental list of things to do within the next
6 months to a year (possibly when I do my timing chain/water
pump/related parts) as time/money allow (and, from the Far Side™
cartoon, we all know that Einstein proved that time was equal to money).

I've never forgotten Dan's advice not to use Bosch O2 sensors on
Chrysler products - will heed that advice when the time comes. I will
probably find my best internet discount DC dealer price, though some
people claim that they are likely to be Bosches. Life's just full of
risks - we've just gotta thread the needle.

Bill Putney
(To reply by e-mail, replace the last letter of the alphabet in my
address with the letter 'x')

 

This guy seems reasonable, dunno if his stuff is what he says it is.. but
you can take a look ,, doesn't cost anything to look.

http://stores.ebay.com/PROTECHGOTITALL_W0QQssPageNameZviQ3asibQ3astoreviewQQtZkm

 

-----------

From:

http://www.allpar.com/forums/lofiversion/index.php/t45540.html

(Oct 4 2004)

Let me be the one to tell you my $40 lesson I learned about Bosch O2
sensors and Chrysler Corp products.

My 2.5L Acclaim was running very poorly - horrible gas mileage, and
until it was warmed up it was bucking and giving me black smoke - it
was the O2 sensor was stuck lean (making the car run rich). I thought
that $70 dollars for a Mopar O2 Sensor on a car with 150k miles on it
was insane! And every other motor head around me told me O2 sensors
were O2 sensors! And Much to the chagrin and the great folks on the
EEK board - I went with a Bosch O2 sensor! Well it went lean on me in
less than 3000 miles! Pretty much their are a lot of people with the
EXACT same experience i had with my acclaim and other Chry Corp
vehicles. Some ppl's go lean right out of the BOX! I cant imagine the
Neons sensors being much differnet from the Sensors in the K-Cars - O2
sensors at least. I ended up buying a mopar O2 sensor wouldnt you know
the car ran PERFECT and my gas mileage shot through the roof! Lesson
learned! NO BOSCH sensors in any MOPAR i own or ever will own!

Im not saying bosch makes bad stuff - im thinking maybe they just dont
calibrate the sensors correctly for Chry Corps standards? Not sure....
I have spoken to only a handful of people on the EEK board where the
Bosch Sensors worked ok... My advice use only MOPAR sensors in a mopar

------------

http://www.carkb.com/Uwe/Forum.aspx/hyundai/554/O2-Sensor

Bosch sensors are notorious as aftermarket replacements on chrysler
cars and probably just as bad on Hyundai. Better stick with the
Hyundai sensor.

-----------

http://oxygen.ecatalyticconverter.c...del=CONC--003&category=All&part=Oxygen+Sensor

Denso (OEM) Oxygen Sensor
Fits: 1999 Chrysler Concorde (same for 2000 300m)
Oxygen Sensor OE Type. Front - 2 Required Rear - 2 Required
Part #: C5010-117235 $60.46

Bosch Oxygen Sensor
Fits: 1999 Chrysler Concorde
Oxygen Sensor OE Connector. Front - 2 Required Rear - 2 Required
Part #: C5010-128464 $65.56

(unknown brand) Oxygen Sensor
Fits: 1999 Chrysler Concorde
Oxygen Sensor. Front - 2 Required Rear - 2 Required
Part #: C5010-144088 $114.75

See also:

http://www.autopartsworld.com/2000_dodge_dakota_oxygen-sensor_parts.html

(Bosch and Denso share same part numbers?)

 

I certainly don't dispute that this is possible, but it certainly wasn't
the case with my van. I record every gas purchase and compute the MPG
of every tank. I can thus see trends in fuel mileage within just a few
tankfuls (to allow the noise in readings to get averaged out). There
was no change in fuel mileage before or after replacement of the oxygen
sensor. And no detectable change in engine performance. The only
difference was that my wallet was lighter and the check engine light no
longer came on.

I had Chrysler parts installed on my van. I don't know what brand they
use, but if figured the original last 160K and that is good enough for
me to stick with a Chrysler part in this case.

Is it just Chrysler products? I got the impression that he just doesn't
like Bosch in general. I've only replaced one O2 sensor myself and that
was on an 89 Acclaim. I believe the part I got was a Bosch and it
worked just fine. No change in driveability and no change in MPG.
Personally, I think DS has some personal vendetta against Bosch and I
don't take his recommendation here all that seriously. If the problems
were as big as he states, we'd have heard about it by now from other
directions.


Matt

 

There's no guarantee that the so-called "OEM" part is the same brand or
built to the same specs. as what came in the car from the factory. I
used to work for a 2nd tier manufacturer. When we had production
fallout that we couldn't ship for use on the customer's assembly line,
we had a special number we called at a particular 1st tier to see if
they'd accept the parts for their dealer downline. Most of the time
they went for it after reviewing the out of spec parameters.

I've heard that the same is now true of body parts. A so-called OEM
part is likely to be made to the same relaxed specs. that a CAPA
certified part is made to, and maybe by the same manufacturer not the
one who made the one that went on at the factory.

Bill Putney
(To reply by e-mail, replace the last letter of the alphabet in my
address with the letter 'x')

 

I have to agree with DS.. before I found this newsgroup I put 5 Bosch
oxygen sensors in 2 different Acclaims (my own of course) with the same
result.. they all lasted about 3000 to almost 12000 miles before the car
started running like crap...didn't know about the Bosch problem. The small
parts store in my neighborhood didn't carry anything else.......finally
ordered 2 Echlin's online.. they lasted (well as long as I had the
vehicles) at least another 40000 in the case of both cars..

I don't have a clue what the problem with the Bosch was.. (at the time they
had a 1 year warranty and I didn't have to pay for the Bosch replacements)
but had to try something different as I was starting to believe there was
something else wrong besides the sensor as the originals lasted about
100000..

 

Well, I have experience with only one Bosch, but it worked fine in my 89
Acclaim. Maybe I was lucky, but I still find it hard to believe that
Bosch can be that bad and still be in business.

Matt

 

Nospam Clare comes up with all kinds of imaginative notions. If you buy
garbage, you get garbage. If you buy good stuf, most of the time you get
good stuff.

No reason to pay dealer markup, just get good NTK ones from www.ngk.com

DS

 

The primary reason for downstream O2 sensors is to monitor cat efficiency.
However Chrysler does use input from the downstream O2 sensors to "fine tune"
fuel trim.

An O2 sensor should be able to switch from <175mv to >800mv. It should also be
able to do it in less than 100ms. Easily checked using a DSO.

Drift is a little harder to detect. With a scan tool, you could watch for large
changes in fuel trim. This is if there are no other possible causes for the
changes. Of course you'd have to know what is normal for your vehicle to be
able to notice changes. Also, trim that indicates a lot of correction could
indicate the O2 sensor is "off".

I agree on the Bosch O2 sensors. Pure crap in a Chrysler vehicle.

 

Will they have some kind of stamp on the box "Crappy" or "Good"?

Hmmm - I drilled down, but, though their home page mentions O2 sensors,
all they show are spark plugs in their drill down.

A google search turned up ngk's web site www.ngksparkplugs.com - I was
able to drill down for the NGK NTK O2 sensor part number 23048. Plugged
that number into the ngk.com site, and they do list it at $60. That's
what I'll go with.

Bill Putney
(To reply by e-mail, replace the last letter of the alphabet in my
address with the letter 'x')

 

How DO you tell the good from the bad?? Buying from the dealer is no
guarantee - even dealer parts have an unacceptable infant mortality
rate in many cases - and jobbers will sell anything - so it doesn't
matter if you pay top buck from NAPA or lowball from PartsAmerica or
PepBoys - you could be getting the same stuff and just paying more. In
the case of O2 sensors how many manufacturers are there? The VAST
majority, whether OEM or Aftermarket are either NTK/NGK or Bosch.

 

I finally broke down and replaced the O2 sensors in my wife's car at
220,000 miles. If I cross my eyes, I *might* notice a little improvement
in drivability, but nothing actually measurable. I know that 02 sensors
get "sluggish" with age, but in my experience it takes a LOT of age to
make them too sluggish to work properly.

 

We replaced the forward O2 sensor in my wife's '97 Voyager (3.3L, 125k
miles) and noticed an immediate improvement in MPG. The MPG had dropped
some months ago, then it almost failed its smog test (high HC), then the
day after the smog test the CEL came on and it put out an O2 sensor code.

So, my experience is that the O2 sensor can clearly be bad (as evidenced
by the poor MPG), without the CEL light showing any problem.