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post #1 of (permalink) Old 02-28-2002, 03:22 PM
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Effects of gutted catalytic in TJ

I have a '97 4 banger TJ. A couple weeks ago the catalytic converter clogged up and I was broke, so I cut it off with a saw-zall, hollowed it out and clamped it back on. Now the 'check engine' light is on. How is this affecting the computer? Is it alright to leave it like this or do I need to replace the cat?

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post #2 of (permalink) Old 02-28-2002, 05:14 PM
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Re: Effects of gutted catalytic in TJ

Yeah you should replace the cat. what may be happening is since the cat is open the senors are getting differnt readings. if your loops back in to the intake then your emssions are alot higher and the engine is wondering why.

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post #3 of (permalink) Old 02-28-2002, 06:01 PM
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Re: Effects of gutted catalytic in TJ

What is happening is where you have hollowed it out your 02 sensors are sending the wrong readings to the pcm. This will cause your Jeep to run a very lean fuel mixture. You need to replace the cat before you kill your 02's as well. Hope this helps.


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post #4 of (permalink) Old 02-28-2002, 06:36 PM
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Re: Effects of gutted catalytic in TJ

Youir '97 TJ is ODB11 compliant. Which means you have 2 O2 sensors. One upstream, ahead of the cat, and one downstream, behind the cat. The upstream O2 is used primeraly for fuel trims, and the downstream O2 is used for performance testing the cat. Your pcm can recognise that your catalyst is inop. This is why the check ingine light is on. Catalyst performance. The only way to turn off the light is to replace the cat and clear the codes. As far as damage to the system, it can wear out your check engine light for being on all the time. It shouldn't hurt your O2 sensors at all, just the anoying light.

FYI, The O2 sensor is way down the bottom of the food chain as far as mixtures are concerned. They are used for fuel trims to correct long term adaptives, then multiplied by load, coolant temp, throttle position, etc.

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post #5 of (permalink) Old 02-28-2002, 08:19 PM
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Re: Effects of gutted catalytic in TJ

If you continually run a vehicle with bad 02 sensors on a OBD2 vehicle it can destroy a cat. The pcm uses the o2 sensors signal to constantly fine tune the fuel mixture so the cat can do what it is intended to do and that is clean the exhaust. So in all reality the 02 is not on the lower part of the food chain. I have seen it many times on numerous vehicles. If the sensor fails to perform it will cause the feedback control system to go into open loop mode with a rich (fixed) fuel mixture. This will cause emissions to rise and the convertor can very well be damaged because it will overheat.


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