2.5L ('98-'01) Upstream Oxygen Sensor Replacement Experience , get the thread chaser!

[dccarpenter]

About a week ago I set about to change my upstream O2 sensor as it was throwing a code , I tried getting it off with a variety of open end and crows foot wrenches and it was not happening even with multiple PB Blaster soaks. I finally got an O2 sensor socket and it took all 220lbs of me and a pipe breaker bar to get it out, the threads on the old sensor were completely toasted.

Of course the new sensor was not threading in after all this, thankfully my old f250 was running well enough to get me down to the parts store for a oxygen sensor thread chaser.

I had to play around with this for a good 10 minutes trying to get it started, finally I got the right angle and gave it several good hard hammer taps to secure it then was able to thread it in using anti-seize on it and making a point to back it out every 3 full turns or so.

The new o2 sensor threaded on nicely after this, I pulled the negative battery cable for a bit and on starting up I was rewarded with no more check engine. About to take a evening drive to see if there is any actual performance benefit.

Just wanted to share this experience so if anyone sets out to do the upstream o2 sensor located on the manifold , buy the oxygen sensor socket and buy a thread chaser to have on hand (at least if it is your only ride that is). I've always had fine luck with my mini torch and pipe breaker leverage for the downstream o2 sockets with no tap/thread chaser needed.

 

[19Walt93]

I bought a big set of thread chasers from Snap On years ago, most useful purchase I've made. An O2 socket is worth having if you're not going to cut off the wire to allow a socket to fit over the sensor. By the way, the "upstream" O2 is the only one you have, the "downstream" one is a cat monitor.

 

[dccarpenter]

I bought a big set of thread chasers from Snap On years ago, most useful purchase I've made. An O2 socket is worth having if you're not going to cut off the wire to allow a socket to fit over the sensor. By the way, the "upstream" O2 is the only one you have, the "downstream" one is a cat monitor.

Unfortunately the cat / exhaust system was cut off of my truck before I got it and I just ran some new pipe from what was left to a new muffler and tailpipe. I was under the impression the secondary o2 sensor didn't play much of a role in computer input/performance. Is that accurate ?

 

[DILLARD000]

I've had good luck with soaking the bung~sensor threads with penetrating oil overnight; makes old sensor break loose relatively easy.
Though I'm out west & don't have the road salt corrosion like in the northeast.

 

[19Walt93]

dccarpenter: With no cat you should have a MIL light on and a code P0420 at minimum. Dillard: If you haven't experienced road salt you're lucky and won't have a concept of how much damage it does, enjoy not knowing. For example, we'd often have to split rotors on 3 year old trucks because they were rusted and swollen and would not slide off the hubs.

 

[DILLARD000]

...If you haven't experienced road salt you're lucky and won't have a concept of how much damage it does, enjoy not knowing...

^ Give thanks daily for where I live\drive.
Hwy dept winter plows here do use MagChloride+Salt but sparingly; plenty of sand\gravel so windshields+headlights are routine maintenance.
As a kid centuries ago, grew up near a drivable gulf coast beach. Dad (a smart man) never drove the beach to us kids disappointment.
Got older & learned to spot vehicles that routinely drove the beach by rusted undersides\panels\bumpers.
My vehicles have a good life; driven+maintained gently, regularly washed inside+out, a warm+dry garage.
D

 

[dccarpenter]

So as Walt correctly predicted, 2 miles after putting in the new upstream sensor and resetting the computer the check engine came back on, guess that downstream one is needed. Is there a negative performance effect from not having it?

I seem to have a bit of a bog/misfire occasionally with the upstream o2 sensor plugged in. When I unplug it , it goes away. I have never had the downstream o2 sensor in the CAT for reference as the cat and entire exhaust were missing when I saved the truck from a local junkyard for $300. They were going to demo derby race it ..).

I've put 25k miles on the Ranger in less than a year and traveled to Maine and Kentucky from Maryland in it, it's been a reliable daily driver with just regular maintenance.