Catalytic / Oxygen Sensor Modification

I am working on a 95 Blazer 4.3 exhaust system. I live in a somewhat rural area and spend a lot of time on washboard dirt roads that have among other things destroyed my catalytic converter a second time (the ceramic does not seem to hold up to the constant shaking). Seeing as I mostly use the vehicle for local use pulling stuff around I decided to just replace the converter with a pipe this time. I left the oxygen sensors intact but as I anticipated the service light came on a day or two later. I am now working on a modification to eliminate the service light in case something more important comes up. I have a very good idea how to do this using a small resistor or diode to slightly lower the downstream voltage but need to know a couple things…

1) The downstream oxygen sensor wire identifications (note: the colors change at the connector); I will likely try to figure this out with a meter but it never hurts to ask
2) The acceptable voltage range between the upstream and downstream sensors with a good catalytic converter installed; I believe it to be around .05 volts but am not certain
3) If anyone else has tried to do this what you experienced, particularly the ratings of the resistor or diode you used

I have searched the Internet for hours but have come up with very little. Any information that you can provide will be greatly appreciated. Thanks

try searching how to test a O2 sensor. that should give you the range of resitance. once you know that and the supply then u can put it in the middle. the only sensor you should have to fool is the after cat one. the one before the cat should be fine. i know what your saying about the cat. mines taking a dump after 10 years of driving in the city. i too would like to just put a pipe in place of the cat. i know they make O2 simulaters so if you also might want to look that up as well. i don't see how a O2 sensor would adjust the mixture to how the cats acting. i don't know it might. if it hasn't set a code after 2 trips and the 3rd time you drive the truck and it hasn't set the code your fine. but the truck has to be cold the 2 times it runs to run the 2 trips. let me know how you make out.

I was able to figure out which wires were which for the downstream O2 sensor today, I will post all the details on the entire prodcedure when I am done. All that I need to know now is how much I need to drop the voltage by. If any one is doing any diagnostic work on their vehicle (or knows by some other means), the number I am looking for is simply the voltage of the downstream O2 sensor (#2) subtracted from the voltage of the upstream O2 sensor (#1) at any given moment. As far as an O2 simulator, by keeping the downstream sensor intact all you should need to do is slightly lower its voltage with a $1 component from Radioshack. If you were to totaly eliminate the downstream sensor however, you would need a simulator. You can buy them for around $40 or if you are up for a project can build one. Here is some info on that:

http://www.clubcivicquebec.com/site/technical/Performance/002.html

I really don't know anything about this as I am trying another more simple approach, but alot of respect goes out to anyone who does this.

well i'd just like to kick the cat and replace it with a pipe. i'd rather not mess with the O2's. let me know what u do.

were you able to figure out the voltages you needed for the o2 sensor to be fooled? I know it has been a few months since your post but I am going throught the same thing right now and do not want to waste my money again on another catalitic converter! Do you need asistance with it?

Umm, instead of going through that you can buy a dummy 02 sensor to fool the ecm from summit... They run about 30 bux...

You need part # CEI-104032

http://static.summitracing.com/global/images/prod/large/cei-104032_w.jpg

Umm, instead of going through that you can buy a dummy 02 sensor to fool the ecm from summit... They run about 30 bux...

You need part # CEI-104032


-----------------------------------------------

Thanks for the reply rlith! Where were you able to get a price of $30? everywhere I have seen was no less than $75..

If It does wind up costing that much would it benefit me more in power and gas miliage to just buy a catalitic converter?? I have a 97 chev Blazer 4.3L

That or you can spend four bucks and about ten minutes to modify your current one.

Go to the HELP! section of your local parts store and buy a pack of sparkplug non foulers. Two of them come in the pack. I don't remember the size, but get the ones with the same size threads as your current o2 sensor. Remove your o2 sensor, then thread one of the non foulers (we'll call this one nonfouler 1) into the hole in your exhaust pipe. Drill out the center of the other non fouler (we'll call this one non fouler 2), so that the o2 sensor will screw into it and not bottom out. (9/16 drill bit I believe). You then thread the o2 sensor and non fouler 2 into non fouler 1. And that's it. *

When you're finished they will be in this sequence: exhaust pipe > non fouler 1 (the virgin one) > non fouler 2 (the one you drilled) > o2 sensor.

This is what a non fouler looks like:
http://img471.imageshack.us/img471/5375/3420025er.jpg

*Disclaimer:
Please only do this temporarily, because running without a cat adds pollution to the environment.

The problem with that blazee is that I believe it's not going to give the proper resistance to the ECM thereby causing the same problems...(Though I agree, better to just use a cat, I got my catco from summit for only 60 bux when I replaced mine, would not want to get busted without a cat, big fines there)

My cat was plugged and the direct fit magnaflow cats from summit have a three week delay in shipping. I gutted my cat and have been running with the above setup for about 2 weeks now, I've driven a little over 2,000 miles and no light yet.

Yeah, there really isn't a reason to remove catalytic convertors anymore, the ones nowadays flow ten times better than the old ones that started the cat removal craze several years ago.

Oh, and a little advice to everyone.... a gutted cat sounds like shit..... can't wait to get the magnaflo on there.

Is it better for the motor to run the exhaust with a cat or does it matter? Things like gas mileage, horsepower, etc..

I had to gut mine because the crap inside started breaking up.