RCPro87

I have a 97 Sport I6. I have a header ready to go on and i plan on doing a full exhaust with 2.5". I dont really want to reuse my old Cat and im probably not going to buy a new one. Since my O2 is in the Cat, do i have to worry about a CEL? or the truck changing its fuel maps, etc. because i just zip-tie the sensor up out of the way? Thanks

BlueXJ

RCP without that second sensor the engine will be looking for the signal and will constantly reading oxygen b/c it is in the airstream. thus a rich fuel mixture is called for by the ECU and a constant CEL. Not a good idea at all. If you want to put a straight pipe in the exhaust then at least weld a bung into the pipe to accomodate the second o2 sensor.

RCPro87

Ok im convinced, just putting it into the pipe wont throw the CEL either? Its kinda just like your cat just stopped filtering out all the crap and its blowing out the exhaust.

SeriousOffroad

It all depends on the exhaust gases. If the sensor signal to the PCM is not within the parameters that are programmed into the PCM then you will get a Chech Engine Light.

Keep in mind that even if you do not have Emissions Tests/Inspections in your neck of the woods, you are still violating Federal Law by removing the Catalytic Converter. Yes you can be ticketed and fined.

The 4.0L is a damn fine motor that will provide many years of reliable performance and decent MPG even in stock form. Save yourself a ton of headaches.... install a cat.

RCPro87

ok one more question for you guys. Should i just keep the old cat or suck it up and buy a high-flow cat? what are your opinions on high flows vs. replacement?

SeriousOffroad

One of my customers runs a reputable exhaust shop here. I talked to him about "Performance" cats a while ago. He said there really isn't enough of a difference between a hi-flow/performance cat and a stock (OEM) style cat. So when I replaced mine I used an OEM style cat from my local parts house. YMMV