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Discussion Starter #1
My son has been doing performance mods on his 2002 Rio and recently put on a new header. Now the wire for the lower O2 sensor is too short. Is there a place to get a sensor with a longer wire or a way to extend the wire?
 

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You can just cut the wires near the plug (about 4 inches away would be good) and extend the wires. If you know how to solder, this would be the best method. If not, just use some butt-connectors. If, by chance, 4 inches from the connector is close to the header, you might have to get closer. The wires from the factory are heat resisant wires so the new wires will need to stay away from the header.

You'll also want to seal the connection from water. Shrink tubing is the best, but good electrical tape will work also.
 

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Thanks for the quick reply. I was told the original wire is stainless steel. I do electronics, so am familiar with soldering, but have never done it to stainless steel. Are there any differences?
 

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Ya, it is stainless. I have two different types of solder, but I can't remember which I used and I don't know for sure that it would matter. I have the 40/60 Rosin core solder and some silver solder. It's been a while, but if I remember right the Rosin core didn't solder the stainless as nice as the silver solder did, but it did work.
 

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Thanks, guys. Unfortunately, the more I learn about this thing, the more I find out that I didn't know. It seems that, when he put the header on his car, he removed the factory manifold catalytic converter. He then took it to the exhaust dealer who put an aftermarket converter under the car. My son says the hole for the downstream O2 sensor is in the side of the new catalytic converter. Is this new converter going to work, or are we screwing with the natural order of things and the computer is going to refuse to talk to us any more? Also, does it make sense that the hole is in the side of the converter? Shouldn't it be after the converter? What would we do with our time if we didn't have children to create work for us?
 

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Here's the way I see it:

I think that the O2 sensor is in the side of the converter to trick the computer into thinking everything is stock. The cat is probably a high flow cat, so the exhaust would be less dense (because it's bigger and the pressure drops), creating the need to move it. If the sensor was located after the cat, it would tell the computer that the car is running lean (because less exhaust is running past the sensor), and the car would send more fuel, making it run rich. By moving it to the middle of the cat, it "sees" that the exhaust is right where it should be.

Bigger cat=less pressure=less exhaust flowing past the sensor=leaner reading

Smaller (OEM) cat= more pressure=more exhaust flowing past the sensor=richer reading

Solution=move the sensor to a place where the reading will be richer=side of converter.

I think that the converter will work for you, but the chance of turning on the check engine light is still possible.

I don't know what else your kid plans on doing to his Rio, but when it comes to computer controlled cars, the more things you change, the better the chance is that the check engine light will come on, even if it runs a lot better. The computers are set to see a given maximum and minimum value for each sensor. When you change something, lets just say you replace the throttle body with a larger one, the car will run richer because you're able to get more air into the cylinders. More air in the cylinders tells the O2 sensor that the car is running lean (because the exhaust is more diluted with air so the O2 sensor senses more O2) and it tells the car to add more fuel. This creates more horsepower, but now the computer thinks that there is a problem because it is constantly sensing that the engine is running lean. If the sensor's output is still acceptable to the computer, then the light won't come on.
 

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Wow, great answer. I'm with you all the way. OK, back to the sensor wire. I'm assuming I can increase the length of the sensor wire by splicing in a piece of copper wire of the same size as long as I keep it away from heat. In other words, I don't have to use stainless steel.
 

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I don't think you would even be able to find stainless wire. Copper is fine, just make sure it's well insulated from moisture.
 
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The O2 sensor located after the catalytic converter does not affect the performance of the engine at all. It only functions to dectect a problem with the catalytic converter's ability to reduce the emissions of the vehicle. I don't see any benefit in putting the sensor in the back of the converter or in the pipe after the cat.

When you splice the wires make sure you stagger them. (i.e. cut them different lengths so that no to splices lay against each other. This reduces the overall thickness of the splice and also reduces your chances of a short circuit in the splice)

Best of luck.
 

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That's true, but if the sensor after the cat switches from lean to rich too often, then he'll get a check engine light with a code P0420.

I guess I just kind of assumed, but he said that the new bung is in the middle of the converter which tells me that there is a brick of catalyst in front as well as behind the O2 sensor. If I'm wrong, and there is no catalyst after the cat, then you're right and it wouldn't matter if the sensor was mounted in the pipe after the cat or at the back of the cat.
 
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