Question on oxygen sensors?

[bowtie_pasta]

I cannot find any information on when these should be changed.  Are these a consumable part that should be changed after so many miles or months/years?

 

I've heard they can get fouled really easy requiring replacement.  Just want to make sure before I part with $25 for a new one.

 

Thx  

[firecadet613]

Don't change it out until you need to.  When it goes bad you'll know.  The SES light will come on.  It's not a normal maintance item like plugs or wires, its more like a CV Joint/Boot, you only replace it when it goes bad.  Save your money.  I've got 97K on my Blazer and it needed a new one at 27K under warranty but thats it.  Been fine since then

 

Joe

[bowtie_pasta]

Thanks Joe!  But this one is actually for my older Blazer (1985), that has been having some trouble.  At high speeds the check engine light has been coming on for a few minutes, then goes out.  Always goes out when I slow down.

 

Plus it's been a little sluggish so I'm thinking the air/fuel mix is off.

 

What do you think?

[CMNTMXR81]

What Joe said.  It's not a normal routine maintanance item unless it is not performing.

 

Chances are, it being an '85, it's not a self heating O2 sensor (look for 2 wires on it) and with high mileage, it probably wouldn't hurt anything if you did change it.  They aren't that expensive.

 

If it is a 4 wire O2, then it's a self heating unit and if you have a scan tool of some sort you can see if it's doing it's job upon initial heating.  This is a tell tale sign of the O2 sensor doing it's job.  If you can scan it, when you turn the key on, it's millivolts (Mv) should start somewhere high like in the .600 to say even .900Mv range.  But within a few seconds should drop down considerably (I have specs at home somewhere I can look up) as the O2 heats itself.

 

A simple and cheaper way would be to pull the O2 you have, clean up the O2 bung as well as the threads on the sensor itself and even clean up the sniffer section of the sensor.  Sometimes after years and mileage, it loses a good low resistance connection and a simple cleaning can do wonders.

[bowtie_pasta]

Well I'll tell you what.  I did have it changed about 4-5 years ago when the check engine light was doing the same thing.

 

It's just a single wire.  I went ahead and disconnected the connector and cleaned it out and put it back together since it was all crudded up with grime.  That same day I got the check engine light on the freeway like normal.  Next day though, no check engine light, which is great!  Today driving to work I noticed it's got quite a bit of pep back.  Well see if it stays consistent when I come home on the freeway tonight.  I wonder if it took a day or so for the air/fuel adjustment to settle in?  

 

Thanks for the help, as usual!  

 

later  :thumb:

[mnstrmdnss]

actually, bowtie_pasta, what they are telling you is bull. single wire o2 sensors should be repalced every 50,000miles, and 4wire o2 sensors should be replaced every 100,000miles because even though you may not get a check engine light, o2 sensors  can "slow down" and not respond as well when they get old cause of the chemical reaction inside the sensor. and the ONLY TRUE way to know if an o2 sensor is working PROPERLY is with an ossiliscope to actually see the smooth fluctuating mv from 50-700mv.

single wire o2 sensors are fairly cheap, anyway.

[bowtie_pasta]

Well, I'm gonna change it for sure soon!!!

 

Thanks for the info!   :thumb:

[bowtie_pasta]

Just as a follow up, I changed it and it didn't take care of the problem.  I'm still getting the intermittent check engine light at consistent speeds above 55mph.  As soon as I slow the RPM's down or come to a stop it will go out.  Along with this I have quite a bit a hesistation while accelerating.  I'm almost thinking I need a new carb.  I had it rebuilt a couple years back.  Who knows???   ???

[cyrylyn]

it sounds like an engine problem.  you should probably take it to someone that know what they're doing rather than replacing random parts and hoping it goes away,

[Colorado Kid]

The last responce begs a question for which I don't have an answer: Where do you find someone who knows what they're doing with a computer controlled carburetor.  I never knew of one that ran even sort of right in the '80s or '90s...who can fix them now?

[CMNTMXR81]

actually, bowtie_pasta, what they are telling you is bull. single wire o2 sensors should be repalced every 50,000miles, and 4wire o2 sensors should be replaced every 100,000miles because even though you may not get a check engine light, o2 sensors  can "slow down" and not respond as well when they get old cause of the chemical reaction inside the sensor. and the ONLY TRUE way to know if an o2 sensor is working PROPERLY is with an ossiliscope to actually see the smooth fluctuating mv from 50-700mv.

single wire o2 sensors are fairly cheap, anyway.

No it isn't "bull!"  I've never changed O2 sensors as a preventative maintanence item.  Only when they go bad.  Yes, they will slow down response over time, but as long as they do their job within normal operating parameters, there is no need to replace them until they STOP operating in those parameters.

 

You also don't need an oscilloscope to monitor them, I monitor them with my laptop.

 

I suppose you change your headlights every 10,000 miles too because they get a little dimmer than what they were when they were brand new!  

[mnstrmdnss]

actually, jackass, im an automotive technician of about 3 years, and as an o2 sensor slows over time, you fuel milage suffers, also. in fact, just yesterday, i had a ford taurus in my shop for a "check engine" light, and the code was a po430, catylist system efficiency below threshold(bank 2), well, even with your cheap autotap laptop system, you would have probably say the o2 sensors working just fine, and condemdend the cats, a $600 mistake! but my Sun engine anylizer confirmed the cats were just fine and the post cat o2's were the problem, even though they wear fluctuating from .1-.9mv. you definatly arent even close to ASE cert, are you?

 

my point, just cause its working(especially an o2 sensor), doesnt mean that its working properly.

[bowtie_pasta]

Here's another thought.  I'm sure I've got the original CAT on the thing.  Is it a possibility that it's plugged?  From what I hear the old 'pancake' style CATS tend to clog up easier.

 

thanks

 

PS - this is just my daily driver so I don't mind tinkering on it, just as long as it keeps rolling down the road...

[mnstrmdnss]

cats can get plugged. i suggest you read this very interesting article, http://www.autotap.com/articles/Intro_to_E..._Systems.htmlue

 

if the link doesnt work, go to www.autotap.com click on "obdII techical library", then click on intro to emission system, it tells all about the cat.

[bowtie_pasta]

That was a GREAT article, thanks for the link!  :thumb:

 

Since I don't smog this bad boy I'm gonna see about having the exhaust redone, with NO CAT.

 

Thanks again.