Question about replacing O2 sensor.

[freewheeling]

I have a 1998 SL2 DOHC. I got that "check engine soon" light just before having my emissions checked (a little before it was necessary) and the fellow at the service station checked the computer codes, which showed a bad oxygen sensor 1 bank 1. He said he could "fix it"... for $395. I didn't actually need the emissions to pass for a couple of months so figured I'd do some price comparisons before diving into that pit. Anyway, shortly after that the "check engine" light went off, so I figured the code might have come on as a result of a rusted muffler that I just had replaced. Anyway, I figured "no problem."

Then it came back on again, about a week later. This time I went to Autozone and they showed the same code (P033, I think) indicating that the O2 sensor 1 bank 1 was "slow to respond." So I asked how much to replace it, and after checking to find that the sensor was at the very front of the vehicle and easy to reach I bought a universal O2 sensor for about $20. (The wire connection looked pretty easy, while the non-universal sensor was about $60.) I also borrowed the special socket removal tool with the slot on the side to make the job a bit easier.

All of that's sort of a long way of getting to the point, which is that even with the special removal socket and a breaker bar *I can't get the sensor to budge*. I was trying it with the engine still hot because I had some idea that it might be easier, and I'm sort of stupid (i.e. there's more mass *around* the sensor to expand, and when it expands it'll obviously make the *hole smaller*, not bigger). So I doused the thing in liquid wrench to see if that will help, and I'm sitting here waiting for the engine to cool...

But while time passes, is this sensor typically a bear to remove? Are there any special tricks I might employ if it remains stubborn? Any pitfalls, such as the possibility of the thing breaking off if I push the breaker too hard? Counter-clockwise-out, right?

Also, just for the heck of it, and assuming I get the sensor successfully changed, is there a trick to turning off the "check engine" light, besides disconnecting the battery, or will it go off by itself after a few miles?

[wafrederick]

You might have to heat it up with a torch until red hot,the thread size is 18mm x 1.50 if the threads get messed up and most parts stores sell this tap since it is a spark plag thread size too.You cannot get any Saturn parts aftermarket,dealer only.Have you topped off the gas tank?If you do this,do not do it and there is a reason why.The evap system is sealed and needs space on OBD 2 vehicles.This wil also set of the o2 sensor code.When it clicks,stop when refilling.

[freewheeling]

Originally Posted by wafrederick

You might have to heat it up with a torch until red hot,the thread size is 18mm x 1.50 if the threads get messed up and most parts stores sell this tap since it is a spark plag thread size too.You cannot get any Saturn parts aftermarket,dealer only.Have you topped off the gas tank?If you do this,do not do it and there is a reason why.The evap system is sealed and needs space on OBD 2 vehicles.This wil also set of the o2 sensor code.When it clicks,stop when refilling.

I generally stop when it clicks, more out of laziness than design, but that's good to know.

Also, I think the heating trick works with nuts because the expanding nut (which has nothing constraining it around the outside) also expands the hole. However, it seems to me that heating the exhaust manifold, which is a big chunk of metal, would only *shrink* the hole. But I could be completely wrong about that.

[freewheeling]

Letting the engine cool and/or dousing in liquid wrench allowed the sensor to come out, with a little persuation from the breaker bar. The wiring splice was easy. Saved me, what... $365? Oy!

[denisond3]

Just for future reference; heating the manifold would have expanded the threads of the hole (outward) where the oxy sensor threads in, since all the metal around it would expand too. So it would work to loosen the sensor from the manifold. I use an oxy/acet. torch for that, as a propane torch doesnt heat things nearly as fast. But using the penetrating oil is good too, and it wont burn up things nearby like a torch flame will. Another stunt is to give the old oxy sensor a good whack sideways with a hammer, at its base. Thats if you can get to it with a hammer. It helps to loosen the grip of the rust between the O2 sensor threads and those in the manifold.
What could they have been planning to do for over $300, even assuming they were going to charge you double the price of a $60 O2 sensor.

[freewheeling]

Originally Posted by denisond3

Just for future reference; heating the manifold would have expanded the threads of the hole (outward) where the oxy sensor threads in, since all the metal around it would expand too. So it would work to loosen the sensor from the manifold. I use an oxy/acet. torch for that, as a propane torch doesnt heat things nearly as fast. But using the penetrating oil is good too, and it wont burn up things nearby like a torch flame will. Another stunt is to give the old oxy sensor a good whack sideways with a hammer, at its base. Thats if you can get to it with a hammer. It helps to loosen the grip of the rust between the O2 sensor threads and those in the manifold.
What could they have been planning to do for over $300, even assuming they were going to charge you double the price of a $60 O2 sensor.

Thanks for the tip about whacking with a hammer. As for what the shop manager was planning, Gawd only knows. Charitably, he might have been thinking of a different kind of vehicle where O2 sensor replacement involves pulling the engine or something else pretty exotic, but I tend to think he was just trying to soak me. Turns out that since I moved south of Quantico I didn't really even need to pass an emissions test, but it's just as well I fixed the thing. I gather that a bad sensor can cause some pretty awful gas mileage as well as other mechanical problems, if you let it go.