2005 4.0 catalytic converters

BigDan

BigDan

TJ Enthusiast
Supporting Member
Joined
Aug 21, 2021
Messages
122
Location
St-Jean Baptiste , Quebec.
2005 LJ ,4.0L ,automatic

My LJ is sluggish on performance compared to my CJ : 4.0L ( obd I ) , gets out of OD at the slightest grade ,
I get a O2 sensor bank2 no 2 code once in a while and after reading some posts here , I removed the whole exhaust system ,,,,,the cats seems ok , no rattling noise , no loose particles , even the look seems great

IMG_9341.jpeg
Does it look ok ?


Other thing ,at the end of the front exhaust pipe near the muffler flange ,is it a third cat or a resonator ? What bugs me is that there is a grid

Thanks
Dan ,

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Yes, all of those are catalytic converters. Luckily, they all look structurally intact.

The oxygen sensors for the computer to measure exhaust gasses and meter fuel are just before and after the smaller first two. The third is just extra.

Have you switched out the oxygen sensors yet?
 
Fulton_Hogan said:
Yes, all of those are catalytic converters. Luckily, they all look structurally intact.

The oxygen sensors for the computer to measure exhaust gasses and meter fuel are just before and after the smaller first two. The third is just extra.

Have you switched out the oxygen sensors yet?
Click to expand...

Yesss rhe one that gives the code ,
But cel came back couple of weeks after ,on/off
 
Has the the LJ been deteriorating over time or did you just get it and it's not performing as well as the older 4.0?

What's the differential gear ratios on both Jeeps?
 
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If you use an ODB reader to monitor the O2s do they range under .9v?

Have you driven it without the exhaust and O2s? It'll throw codes but run on basemap...if you see an improvement then you're on to something with the cats.

-Mac
 
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macleanflood said:
If you use an ODB reader to monitor the O2s do they range under .9v?

Have you driven it without the exhaust and O2s? It'll throw codes but run on basemap...if you see an improvement then you're on to something with the cats.

-Mac
Click to expand...

Mac, without the exhaust system ?
Cant do it , cops will jump on me ,
 
1). Can I remove the third CAT that is just before the muffler without any issues ?
Id put a stainless pipe instead ,I have to replace the catback muffler aniway

2) the exhaust manifold is cast iron , would there be a REAL gain by replacing with a tubular one ?

Thanks 🤗
Dan ,
 
BigDan said:
1). Can I remove the third CAT that is just before the muffler without any issues ?
Id put a stainless pipe instead ,I have to replace the catback muffler aniway

2) the exhaust manifold is cast iron , would there be a REAL gain by replacing with a tubular one ?

Thanks 🤗
Dan ,
Click to expand...

You can remove the third cat without any issue.

As for replacing the exhaust manifold for say longtube headers, there wouldn’t be any gain without further modifications ie tuned. Though the gains wouldn’t be significant enough to pull the trigger. The money it would cost you’re better off hitting up Flying Ryan for one of his base tunes or better yet re-gearing (pending on your tire size and current gear ratio).

*Edit, after reading your profile for the LJ you’ll want to re-gear your rig to 5.13 for 33” tires first. Here’s a gear chart used by forum members for reference.
 
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I’ m putting some 4:10 gears on with an e-locker
The gas is over $6.00/gallon in my region

My 86 CJ with a 99 4.0l ,ported & shaved .030 head combined with 4:10’s gives me exactly what I want ,
 
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