Rounded off Oxygen Sensor

bacelaw · Nov 5, 2006

Ok - so in hopes of increasing my mpg's i have completely rounded off my 10 year old oxygen sensor - it's the one coming out of the catalytic converter...

any ideas on how to get it out now???

thanks

BIGSLVRXJ · Nov 5, 2006

bacelaw said:
Ok - so in hopes of increasing my mpg's i have completely rounded off my 10 year old oxygen sensor - it's the one coming out of the catalytic converter...

any ideas on how to get it out now???

thanks

Can you hit it with pb blaster and vice grip it?

mpro1 · Nov 5, 2006

Heat with torch until slighty red use vice grip. Then replace with new one

you should have heated it up in the first place

bacelaw · Nov 5, 2006

Yah, i dont have access to a torch - so i ran the vehicle for a while to heat up the exhaust...i pb blasted it, i was careful....vice grips wont really hold now either - it's THAT rounded...

are there any special tools i could use?

JohnX · Nov 5, 2006

A torch is the answer. Visegrips WILL turn it, it just a matter of getting them tight enough. Find someone with more grip strength to put them on and turn them for you. If they are old and the teeth are flattened out, then get a new pair...and get the good ones, not cheapos.

bacelaw · Nov 5, 2006

good advice, i do have el cheapo vice grips - the teeth are showing some wear.

but aren't there tools for this? special rounded bolt wrenches?

5-90 · Nov 5, 2006

You don't need much torch - a regular plumber's torch (like you get at the hardware store, that takes replaceable prefilled gas cans) will serve. You're not trying to weld - just make the metal expand.

5-90

JohnX · Nov 5, 2006

I have a set of stud removers that would work well, but they don't go big enough to get around the OX sensor. Sometimes a hammer and a punch/chisel works pretty good. You have to drive it at just the right angle to turn it without slipping off the side.

bacelaw · Nov 5, 2006

i just found some sockets with teeth inside them at amazon.com...but they don't get to 7/8.

i will buy a plumber's torch and a new set of grips.

do i torch the base of the sensor?

5-90 · Nov 5, 2006

No. Torch the hex "knuckle," and that will expand the threaded part of the sensor without really expanding the bung - which is what you want.

While you're out and about, get a block of "canner's paraffin." When you've got the sensor knuckle heated up to a dull red or better, touch the paraffin to the junction between the sensor and the bung. The paraffin will melt and wick into the space between the internal and external threads, and give you a little more room to loosen the sensor. Make sure you clean/burn all of the paraffin out before installing the new sensor, since it wants a ground. Also, make sure never-seez is on the sensor threads - put it on if it is not. Torque to 20 pound-feet with never-seez.

5-90

Blaine B. · Nov 5, 2006

The sensor coming out of the cat does not affect fuel, that is the one on the downpipe. Sorry to burst your bubble.

bacelaw · Nov 5, 2006

actually, i don't have a oxygen sensor in the downpipe - it's a '96...and why wouldnt a cat oxygen sensor that's 10 years old not affect mpg?

Blaine B. · Nov 5, 2006

OBD 2 has 2 sensors for sure...... (1996 +)

Cat oxygen sensor tells the computer how the emissions are, and to let you know if your cat is failing. The first one affects fuel mixture; not the second.

NighthawkXJ · Nov 5, 2006

why do you not have one in your down pipe? I have a 97 and it has both, and reichy here in town has a 93, and the only one he has is in the down pipe.

Did i miss something, or did jeep stop putting them in the down pipes between 93 and 97?

5-90 · Nov 5, 2006

Because with OBD-II, HEGO sensors were used in two places.

One was used at or near the exhaust collectors - this sensor is used to adjust fuel trim (like always,) and will therefore affect fuel mileage and efficiency.

The other would be used after the catalytic converter (each, if you have two) and is used solely as a check of converter function. This has nothing to do with fuel trimming.

So, if you're having fuel issues, you'll really want to start with the "upstream" HEGO sensor (the one forward of the catalytic converter) rather than the one after it...

5-90

Blaine B. · Nov 5, 2006

Indeed.

bacelaw · Nov 5, 2006

i cannot find a sensor in my downpipe - the only one i see is the one sticking out of the cat converter.

5-90 · Nov 5, 2006

The bung for the upstream HEGO is usually in the exhaust manifold proper, just ahead of the collector (where the downpipe bolts on.) If it's not there, I've sometimes seen them in a pipe bung just forward of the catalytic converter, but they're usually as close to the engine as possible, so they heat up faster.

You should be able to find it in the exhaust manifold in a location where it can sample all of the exhaust gas at once - which is why they're usually in the collector.

5-90

Blaine B. · Nov 5, 2006

Right, I've never heard of one on an XJ NOT being there.

bacelaw · Nov 5, 2006

are both oxygen sensors the same? that is, the foward and the one on the cat, are they interchangeable?

Rounded off Oxygen Sensor

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