Catlytic converter question
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Fleet Mechanic
Joined: Mar 2005
Posts: 1,603
Likes: 1
From: St Louis
Catlytic converter question
My 91 bronco has a problem with the cat being that it simply is not working and not passing emissions testing. I have tried to figure out if my exhaust is a dual cat or a single cat system orginally from the factory. I think the original factory y-pipe is in place so I do not see a placement for a second cat, and the cat was cut off once and replaced some time ago. How do I figure out if my bronco needs two cats? If it doesn't I am considering just getting a premium quality cat that is of universal fit to replace the non-functional cat. Any help in figuring out how to fix my emissions problem would be greatly appreciated.
Senior User
Joined: Dec 2006
Posts: 135
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I dont know the specific answer to your question. But I do know with a new cat it will burn most everthing. I put a single generic cat on my f150 that had failed smog and when retested it had virtually 0 emissions.
Posting Guru
Joined: Oct 2005
Posts: 1,017
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From: Longwood, Fl
93 cats
My 93 5.8 has two, replaced the second one with a 3" one. Original was pathetic. The first, part of the "Y" pipe may be called a pre-heater--dont know for sure. Air pipe is before both. Also cut angled pipe (~12" long) right behind first cat and reangled it further away from E4OD toward frame.
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Fleet Mechanic
Joined: Mar 2005
Posts: 1,603
Likes: 1
From: St Louis
Mine was just a single cat. I guess the dual cats may have been a california option. Anyway, the cat that came off was 2 1/2" inlet and out lets. The pipe was 3 inch on the inlet and 2 3/4" on the outlet. A fine mess indeed to find ones self in. I bought a universal 3" inlet/outlet cat, it was also much longer than the cat that was already replaced once. Basically I just expanded the inlet to slip over the engine exhaust pipe and then put the rear exhaust pipe into the outlet of the cat. I need to weld the pipe up, since I did not use the expander to straighten the pipe out, so there is a little exhaust leak in places on the pipe that the clamps will not seal. It was a pain in the neck to say the least.
More Turbo
Joined: Oct 2004
Posts: 621
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From: Marana, AZ
On my 91 S/A I have a pre-heater that both exhaust pipes go into and then into a cat. I put a 3" in and 3" out universal cat and ran 3" all the way to the rear. Bronco runs great now! I used a Flowtech 3"/3" Terminator muffler in between. Sounds a lot like the stock Dodge trucks.
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Posting Guru
Joined: Oct 2005
Posts: 1,017
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From: Longwood, Fl
3" exaust
Yea, desertdave35 sounds just like what I did. Same Y-pipe setup also. Replaced 2nd cat with univ 3" I/O. Dont know what brand the muffler is, but it is a round one. 3" single over axle. Really want to try a dual out muffler (2 1/4 or 2/12) and split to each side after axle. I seem to notice some pressure pulses (?)not really a drone, from the one side setup. Maybe the separate outlets would quieten that a little---who knows. Got a rust hole in the tailpipe at the axle. Parts stores carry "Dynomax" mandrel bent pieces for that. Sure isnt cheap but I need to do something soon.
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