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‘95 Bronco XLT 5.0 E4OD, MAF——‘95 F150 XL 4.9 M5OD 4x4, SD
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Discussion Starter · #1 ·
In my half ton with the 300 ive got quite a few holes in my exhaust. in the second CAT and in the muffler and in pretty much every joint is rotten and needing replaced.
will deleting the second cat trip a trouble code or cause any other issues or will it be fine? id like to eventually run 3" exhaust from the first cat back with a turbo muffler and still exit behind the passenger rear wheel. but curious about this first.
 

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1984, 300 L6, smogless, manual 3speed with overdrive.
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2,647 Posts
What year is the 1/2ton, my 84 300 don’t have any emissions on it

edit: nvrmnd it’s in your avatar area 😝
I’d have no clue!
 

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Charlie don't surf..
'92 Ford Bronco XLT
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16,435 Posts
The 02 sensor is in the 1st cat, so removing the second shouldn't be a problem. Having said that, if that 2nd cat is in that bad a shape the 1st is probably bad as well. I'd remove them both and replace with a good 3 way cat from mangnaflow. That's what I did.
 
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1991Bronco 5.8L, w/95frontclip, 6"Superlift/SuperRunner, Deaver J40 springs, 35x12.5 K&N, 3"Bassani
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778 Posts
Doesn't the 5th gen have a 2nd O2 sensor in the secondary cat? I have a 91 which only has a sensor in the first cat in my Bassani Y Pipe. I eliminated the secondary cat and never tripped a CEL and always passed the emissions sniff test.
 

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‘95 Bronco XLT 5.0 E4OD, MAF——‘95 F150 XL 4.9 M5OD 4x4, SD
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373 Posts
Discussion Starter · #5 ·
The 02 sensor is in the 1st cat, so removing the second shouldn't be a problem. Having said that, if that 2nd cat is in that bad a shape the 1st is probably bad as well. I'd remove them both and replace with a good 3 way cat from mangnaflow. That's what I did.
Just spent a few minutes under the truck after getting home from work. Second cat doesn’t appear to have an O2 sensor. There is a pipe providing air from the emissions system fitted in between the two cats though. (I think that’s what it does... I didn’t look at what was on the other end)

I could only feel a leak in the joint after the second cat, but I’ll have to look again in the morning for leaks to double check since one of the only good things about cold weather is it makes it easy to find exhaust leaks. I know I have seen more leaks before than what I could feel just a minute ago. What bugs me most is I have what sounds like a manifold leak... not surprising lol, but I only hear it when driving and under load. I can’t hear it or locate it at idle in the driveway, and when doing a cold start I couldn’t see it either. Is it possible that it’s not an exhaust leak, but something else?
 

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‘95 Bronco XLT 5.0 E4OD, MAF——‘95 F150 XL 4.9 M5OD 4x4, SD
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373 Posts
Discussion Starter · #6 ·
If i take out the second cat and find that it is bad then I will see about a new y pipe w/cat... but the main train of thought for me here is it looks like 3” inch pipe between the two cats so if I delete the second one it’s already set for running 3” the rest of the way.
 

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1995 Eddie Bauer Bronco 5.8L, E4OD, Manual Warn Hubs, Auto Transfer case, 3.55 open diff, 31” BFG’s
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If i take out the second cat and find that it is bad then I will see about a new y pipe w/cat... but the main train of thought for me here is it looks like 3” inch pipe between the two cats so if I delete the second one it’s already set for running 3” the rest of the way.
If it's OEM exhaust, it wouldn't be 3" pipe...I'm not exactly sure what diameter it would be but more in the range of 2" - 2 1/4" id.
 

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Charlie don't surf..
'92 Ford Bronco XLT
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16,435 Posts
Just spent a few minutes under the truck after getting home from work. Second cat doesn’t appear to have an O2 sensor. There is a pipe providing air from the emissions system fitted in between the two cats though. (I think that’s what it does... I didn’t look at what was on the other end)
Ok, that's the air injection tube you're seeing. If the condition of the rest of your exhaust is that bad, I'd expect you have some leaks there as well.

I could only feel a leak in the joint after the second cat, but I’ll have to look again in the morning for leaks to double check since one of the only good things about cold weather is it makes it easy to find exhaust leaks. I know I have seen more leaks before than what I could feel just a minute ago. What bugs me most is I have what sounds like a manifold leak... not surprising lol, but I only hear it when driving and under load. I can’t hear it or locate it at idle in the driveway, and when doing a cold start I couldn’t see it either. Is it possible that it’s not an exhaust leak, but something else?
Exhaust leaks are annoying and can be hard to track down. sounds to me like you have multiple areas that are compromised..I'd start at the top of the system and inspect the exhaust manifolds first. If they're the original cast iron, you may have some cracks in them. That's common.
 
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‘95 Bronco XLT 5.0 E4OD, MAF——‘95 F150 XL 4.9 M5OD 4x4, SD
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Discussion Starter · #9 ·
If it's OEM exhaust, it wouldn't be 3" pipe...I'm not exactly sure what diameter it would be but more in the range of 2" - 2 1/4" id.
it may not be the original y pipe and cats, i dont know... but i know the few inches of pipe between the cats is definitely not 2-2.25" its at least 2.75"
 

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arent there no 02s past the cat except on 96 ob2 trucks? the pre cat ones do all the engine management the after cat 02 does nothing but tell you if the cat is working or not. you can put a 02 spacer in and then it will not throw a cel but i think its like my 90 and they are all before that cats anyway.
 
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