O/T Catalytic Converters - The O2 sensor trick

Let's say, hypotheticly, that someone's catalytic converter fell off on the way to work yesterday, and the vehicle in question (for this example let's say a 1998 S-10 2.0l with 160,000 miles) isn't worth putting any money in to.

Now, assuming that our hypothetical vehicle owner lived in a state with no emissions tests, like maybe Michigan, and was morally flexible enough to live with himself after intentionally disabling emissions equipment... how would this imaginary fellow go about fooling his 02 sensor into thinking everything was OK after he put straight pipe in where the cat was?

I searched around but couldn't find any threads, but I know that somebody in our grand family of miscreants must know the secret O2 trick. I had heard of threading a spacer in to take the O2 sensor out of the direct path of the exhaust, but that doesn't seem right. I have heard that you crimp the end of the O2 sensor, but that doesn't seem like it'd work either. I searched an s-10 forum too, but those goofs all buy little secret devices that look like runtz, and that leads me to believe that it's just a resistor.

Er, I mean, it would lead our hypothetical fellow to think that!

 

Unless there are O2 sensors, you don't have to do anything. If it has one, which a 99 might, it is before the converter, so it doesn't "need" the converter to do it's job. If you eliminate it, the computer will go into "limp home" mode. That is, a fixed timing, and fuel curve, which translates into less power, and bad fuel economy.

 

I was hoping that the O2 sensor was before the cat, but it's not. It's right after it.

 

Putting the resistor in will only give you shit gas milage and a minor performance gain. Does the car have two O2 ssensors, or just one? If it just has one, and it is a before cat O2 (plugged into the exhaust before the cat, or right in the begining of the cat) plub that bitch back in and leave it. The O2 sensor tells the engine how much fuel to give it. if you have two, try pluging the pre-cat one in, but using the resistor on the after cat one. It might work. I don't know a whole lot about these trucks, but there are plenty of S-10 forums that probably could answer your question.

 

Just drill a hole in the pipe that you are putting on, weld in a bung [from any muffler shop] and screw in the 02 sensor. It doesn't know the converter isn't there!

 

O2 sensors are little more than a resistor. A common trick in the Mustang world when a non-catted exhaust i sused is a MIL Eliminator. Basically it tells the computer the O2 sensor is in range. So no MIL. They are realitively cheap and you may even be able to modify one or make one.

 

It's got one O2 sensor, after the cat. I tried an S-10 forum but didn't find much, and some of the opinions seemed pretty... uninformed? Bordering on superstitous? So I thought I'd try the HAMB because there are some crafty devils on here.

Anyone?

 

I guess that makes sense. The cat is just an element that gets really hot and burns off any unburned gasses, from what I understand (which ain't much) right?.

Anyone else got any info?

 

As with any other OBDII vehicle (96+ in most cases) you have at least one 02 sensor before, and one after the cat. It measures catalytic efficiency. You can "trick" the computer by putting in an 02 simulator which basicly just sends the computer an "all ok" voltage so that the computer thinks the converter is still there.

 

Yes. O2 thing supplies voltage--so find out what voltage=good, make up some kind of reducer/regulator that reduces 12 to that small number. Don't thgink a resistor is the way--you want something regulated. According to my readings, an O2 sensor is actually a battery using the air going through as its fluid element!

 

O2 sensors operate in the 14 volt range, using tenths of voltage to report their readings to the ECU. Example, 14.1, 14.4, etc.

 

You know what, it does have 2 sensors. I just crawled under for a look and there's one in the exhaust manifold too.

Does cutting out the cat really effect the O2 readings that much?

 

Yes removing it really makes a difference. At least to the post cat o2. It is only there to determine cat efficiency. As said above you can install a O2 simulator. It is a little more involved than just a resistor. Try a local speed shop anyone there with injection and obd2 1996 and newer will know just what you need.

 

sorry for the hijack, if you run you car long enough in limp mode can the converter become pluged? my GF's car started loosing power over a 2 week period till now it will only idle. the tail pipe is black as hell. i bet you can find a used cat at a junk yard for dam near free.

 

Used cats are bringing up to $75 for the big one for the scrap value of the paladium in them.

 

If its high mileage on both o2 sensors then this might work....Put a new one upstream and leave an old one downstream.The PCM compares the readings from both and if they are the same then cat burn through has occured. If the old one is lazy meaning its slow to switch then compared to a new one the switching rate may be different.A new one upstream may switch faster than the old downstream which would be a normal pattern.The PCM may not realize the cat isn,t there.

 

You can bypass the sensor. Take a look a this:

The first sensor looks for A/F ratio and adjusts accordingly. The second sensor compares the readings from the first to the gasses after the converter. The ECU then makes a determination whether the cat is working ok. It amy also determine wheter or not to turn on the secondary air injection pump, activate the EGR valve, or some other adjustment. If the readings are not within spec, a MIL code is set and the check engine light will come on. The system also looks at the O2 heaters to see if those are working, so if you unplug it or cut the wires, you will probably get a code. It's not as simple as "adding a resistor" or moving the sensor to a different location.

 

what if you were to relocate the rear o2 way back on the exhaust, like just before the rear diff.?

 

Call Dundee Truck & Trim and ask Howard if he's got one. He's in Dundee just off of M50 on First Street. He has a Chevy only junk yard and his prices are exceptionally reasonable. All my S10 junk is too old but I might have a 'close enough' cat. Give me a call tonight and I'll go look at it, it would be in the Sedan Delivery up by the barn.

 

Wrong.
An O2 sensor "makes" voltage. According to the amount of oxygen in the exhaust stream. Zero to One volt, on a factory system. Tells the computer if the car is running rich or lean, so the computer can control the fuel injection (or CCC carburetor) to a stochiometric ratio (14.7 to one air-fuel ratio).
The car 'should' have an O2 before the cat. That way it reads the exhaust gas as it exits the engine. OBD2 cars have one after, so the computer knows that the converter is working correctly, or it throws a code for you to look at it, or to fail an emissions test (the plug-in one, not the sniffer).
Sounds like your system is a bit messed up. It isn;t hard to fix it though.
The trick with the O2 sensor 'resistor' or technique to fool it, is probably to make the computrer think the converter is OK, even if it is hogged out or missing. Don't know much about that.

 

ok ok first off, your truck is not a 2.0...its a 2.2 if its the 4cyl.. and it has two O2 sensors...One of them is in the manifold and one is post cat... AND the only reason the second one is even there is to check on the condition of your cat.. So your PCM will eventually see that there is a problem and that it is free flowing with no catalyst... and set a code and your Service engine soon light will come on. They make dummy o2 sensors to correct this..look in summit or jegs.. or search for MIL eliminators.. they are over a hunert bux I think... You can prolly get someone to retune your PCM to turn off your rear O2 sensor.. I had my 04 z71 done this way when I dualed it and got rid of the cats. But since your not wanted to spend money...just deal with the fact that your SES light is goin to be on. Odds are your wont even notice a difference..

 

O2 sensor needs to be close to the exhaust manifold to work properly. It would not get the proper heat.

 

Probably won't work. The sensor has to reach a certain temperature before it starts to work. The closer to the engine, the better.

 

oh and they read in MVs... like 100-850 mv constantly bouncing between there is normal

 

thats not true for him..his O2 sensors are heated...

 

It is against federal law for a junk yard to seel catylitic converters to anyone but a recycler

 

a friend of mine showed me the trick to fix these type problems, many years ago. You get a piece of black electric tape, and you cut it to fit over the "service engine soon" light on the dash, and then you don't have a problem!

the only problem is that the computer senses that the cat isn't working, so it sets a code, but it still runs ok, doesn't it? so all you need to do is trick yourself into thinking that all is well.

 

OR if you are really nice I can log onto GM dealerworld and get you a wiring diagram and pin location and number so you can remove the terminal that powers your check engine light...

 

Don't believe it man. If your O2 isn't reading correctly it won't give the PCM the correct info and the engine will not run correctly. (i.e. power drop, run rich, poor mileage, etc)

Look here :
http://creativeelectronics.edu.ms/

The company I work at sells performance parts for Vipers and we use the O2 sims from this company when we delete the cats. Never had one of thier sims go bad and good prices.

 

Wasn't Paladium some guy in an old TV Western show?