Why are my O2 sensors lasting so long?

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

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

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.

Correct

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.

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!"

Sure.

Yes.

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

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.

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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

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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:

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

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

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 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

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

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.