OT- oxygen sensor head scratcher..

Hey

I replaced the exhaust from the cat back on a friends Cavalier. A couple of days later he gets a CEL, we read the code and its a PO137, 136 (rear sensor bank 1). Anyway, we take a good look, find a chaffed wire, protect that with some rubber tape, wipe the code and figure we're in the clear. Code comes back after 3 days so we figure that the sensor is bad. I ask him to hit the sensor with some pb blaster for the 2 days before we install the replacement to help remove the bad sensor. I order the part, which arrives today. Anyway, my friend calls and says that after spraying pb blaster on the sensor the code just this morning went away?!

Got me wondering if the sensor was dirty or maybe when we replaced the exhaust there was some crud in the pipe that got blown out or...

any thoughts?

Presuming the old sensor is properly installed, the PB Blaster shouldn't have affected the portion of the sensor inside of the exhaust.

However, the *exterior* of the sensor needs a vent for the sensor to operate properly (in reality, it's comparing exhaust oxygen content to outside air oxygen content). Is it possible that the vent had been blocked, causing the error - and the PB Blaster cleared it?

Even with that possibility, it's my understanding that O2 sensors don't like contamination on either side of the sensor. If the PB Blaster solvents cleared the vent, the oils in PB Blaster will now probably contaminate its internals - and the error will return. I'd replace the sensor.

Further info: In my experience, O2 sensors are remarkably durable. The sensors in my '00 Windstar haven't been touched at 150K+ miles.

I agree Phil... I'm thinking that regardless I'm going to suggest we replace the sensor, particularly as we've got the new part now. I agree too that (touch wood) the windstar sensors seem to last a pretty long time. I've done a few little exhaust things on my van, mostly hangars and flex pipe (2 of those) but no trouble with the O2 sensors.. Hopefully I haven't just jinx'd myself now!

Yeah, I almost hated to even mention my Windstar exhaust.

Mine has been pretty good - still on the original flex pipe! - but I believe the flex pipe is leaking. I've also replaced some of the rubber hangars.

I recently replaced the flex pipe on my Contour. It took longer than expected - and I still have a leak - so I'm not big on DIY exhaust work right now...

I hear ya Phil.

Here's a component that I used on my friend's cavalier that made the job much easier. 47807

it makes the job way easier than trying to drill out studs etc.Had I known about this when I did my last flex pipe I'd have been much quicker!

If it works, you can't fix it!
Consider Buy it yourself parts, and let the local muffler shop do the install labor.

piper -

As it turns out, my Contour uses a flex pipe that has a 3-bolt flange on each end - so no donut-gasket joint or such issues to deal with.

I used an nut splitter to remove the nuts without cutting the studs. Note: The cheap nut splitters you find on-line work - but aren't really up to the task.

Unfortunately, I ended up drilling out one stud - but was able to re-use the rest. But I think the manifold flange ended up with a slight bend that resulted in a gasket that didn't quite seal. I could probably pull it apart again and fix it, but it's time and energy I don't have right now.

Meanwhile, the experience has led me to simply leave my Windstar's flex pipe alone for the moment.

so I just thought I'd update everyone that the bad O2 sensor was indeed the problem. On replacing it all DTCs are gone. I got it from this place http://www.primechoiceautoparts.ca/ (http://www.primechoiceautoparts.ca/)

It was a direct fit and very inexpensive. Off shore product but fit and fxn was great. I did have a bit of trouble getting the old O2 sensor out, and did have to chase the threads with a thread chaser (tap) once out. I was lucky that the new one went in. Anyway, I looked the next day at walker and found this segment of exhaust pipe. http://www.summitracing.com/parts/wlk-41821

Then next time I have to do an O2 sensor replacement I'm going to have this little bit of pipe on hand, along with the 2 clamps it'd need. I mention this in case someone is faced with the same job. Successfully unscrewing an O2 sensor, despite what you'll see on youtube, is a job that will quickly go downhill...

fwiw, my 2 :2cents:

Thanks for following up and sharing your experience!

Yes, I'm familiar with jobs that seem to quickly get complicated...

Out of curiosity: Where did you find a thread chaser the size of your oxygen sensor threads?

It's a Lisle product. As I'm in Canada, I got it at Princess auto, tho I'm sure you could find it at many autoparts places. It's this one, and worked really well.
http://www.princessauto.com/pal/product/8149593/Engine-And-Transmission/Oxygen-Sensor-Thread-Chaser

I wouldn't attempt the job without one. From what I've read, the threads are the same on most "normal" O2 sensors.

Thanks for the info!