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Old 10-09-2014
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3.0 post cat o2 sensor resistance?

I need to know how many ohms it takes to satisfy the post cat o2 sensor. removing my cat and I am going to solder in a resistor to eliminate a cel on a 1999 3.0 flex fuel
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Old 10-09-2014
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Won't work.
O2 sensors are active, they send .1-.9volts back to computer so it can compare it to the upstream O2 voltage levels, this shows the computer that the Cat is working to clean up any unburned fuel.
If downstream O2 has a fixed voltage then CEL will come on because that is a sign that an O2 sensor has failed, it isn't switching voltages.

Cats don't hurt performance, but are expensive to replace, universal Cats are less money and do work just fine.

If you are in the US or Canada there is a $2,500 federal fine for running vehicle on the street without Cat.

I don't want to encourage removing a cat since my grand kids have to breath the air we leave behind................but what might work is to install the downstream cat where it gets a mix of exhaust and fresh air, that will give it the higher Oxygen reading but still switch voltages as computer richens and leans out the air/fuel mix.
Never tried it so maybe it won't work.

Last edited by RonD; 10-10-2014 at 12:08 AM.
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Old 10-17-2014
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My appologies to those that may find this post "anti catalytic removal"; it's not intended to be that, but rather a helpful warning. I would strongly recommend keeping the caalytyic converter you remove, as you will want to re-install it before you sell the vehicle. Please check your local, state, and federal laws before considering the removal of any federally mandated part on your automobile.

My son removed his catalytic converter on his Subaru WRX Sti a few years back (no longer living under my roof), as he was "told" he'd gain a tremendous amount of HP due to its restricting the exhaust flow (bunk). He also had his computer reflashed to remove the CEL code it was setting. He sold the car a year later. One week after selling it, he was presented legal papers by the person who purchased it; they were unable to register the car in the state they lived in, as it required a catalytic converter. So, my son had two choices, pay a hefty fine (much, much larger that the $2500.00 RonD speaks of), or buy the car back for its purchased price. My son obtained some legal advice on the issue, as he had the seller sign a paper that said the car was sold "as is". My son was told this clause did not mean anything in the way of removing federally mandated equipment on a vehicle. A car cannot be sold legally without it's federally mandated equipment installed. A buyer can legally come back to you and require you buy it back, pay to have the equipment installed, and/or you pay a large fine. Local laws will not cover you, even if you do not have visual or "sniff" inspections, federal law supersedes local laws/requirements, as was told to my son from his legal advisor.

He bought the car back (cheaper then the fine), installed a catalytic convertor, and still has the car today, as he had a huge case of sellers remorse anyhow.

Last edited by bucko; 10-17-2014 at 07:14 AM.
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Old 10-17-2014
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Good story and good advice
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