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Author Topic: Cat Issue  (Read 1873 times)

Offline B1G5EXY

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Cat Issue
« on: December 16, 2009, 05:07:09 pm »
Well the wife has an 01 Durango 4.7L with about 104000 miles on it.  We haven't had any issues with it since we have owned it (which hasn't been too long) but yesterday she was on her way home from work when she got to a stoplight and the D just died.  She started it back up and went on her way.  The fuel filter is new and the K&N is clean, so I made my way to the back and that exhaust smells rotten and by the look of it the Cat is OEM.  Can anybody enlighten me on the ramifications to the vehicle if I cut it off and straight pipe it?  We are in Oklahoma so I ain't overly worried about the emissions issue and the cabin noise is something she could live with I am sure but are there any OTHER issues I should know about?  Appreciate it y'all!
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Offline spencea15

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Re: Cat Issue
« Reply #1 on: December 16, 2009, 05:15:40 pm »
The 4.7 do not run right with out a cat.  You will want to replace the o2 censers also since there is most likely one bad but not giving a cell.
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Offline shrpshtr325

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Re: Cat Issue
« Reply #2 on: December 16, 2009, 11:53:50 pm »
i have never heard of 4.7's running badly without a cat on there, BUT the 4.7 does not have one cat, it has two, (at least every one i have looked at), one on each side before the Y-pipe

btw dont trust spencer he drives a v6 gasser and doesnt know about the big boys and the v8s :D
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Offline 04cumminsram

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Re: Cat Issue
« Reply #3 on: December 17, 2009, 12:35:06 am »
y couldnt you straight pipe it then fool the o2 sensors with resistors?

anybody know how many ohms one is supposed to have?
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Offline Kilch123

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Re: Cat Issue
« Reply #4 on: December 17, 2009, 12:43:54 am »
actually, they generate milivolts, and swing from like 400mv to 500mv (normally)

His problem will likely be with the downstream one not seeing a difference from the upstream (if it has them before and after the cat)
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Offline B1G5EXY

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Re: Cat Issue
« Reply #5 on: December 17, 2009, 02:15:52 am »
Man I remember how easy it was to cut the cat and mufflers off of my 83 Z28 and how much of a sound and power difference it made.....nothing is easy any more!
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Offline shrpshtr325

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Re: Cat Issue
« Reply #6 on: December 17, 2009, 05:34:02 am »
Quote from: Kilch123 on December 17, 2009, 12:43:54 am
actually, they generate milivolts, and swing from like 400mv to 500mv (normally)

His problem will likely be with the downstream one not seeing a difference from the upstream (if it has them before and after the cat)


this is correct, you can get "simulators" for the post-cat sensor but they dont really work that well, and the pre-cat sensors are partly responsible for the a/f mixture while the truck is running and warmed up
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