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Discussion Starter · #1 ·
Howdy y'all. I've got a couple codes, P0304, which is cylinder 4 misfire, so I know I gotta replace at least the plugs. I also have a P0420, which I think is clogged cats. My plan is to replace the plugs with Autolite XP985, and replace all 4 O2 sensors with NGK. Here is the part that is confusing me...

I have called Flowmaster and they dont have a cat system for an '03. I took it to a local muffler shop I've dealt with forever, and he quoted me with an AP system, that was all one pipe that included all 3 cats, saying over $500 just for the unit. I called AP, after looking at the site, and they say they dont have a unit that is all one piece, and want to sell the 2 cats individually.

I found an AP unit, part number 645174, but says its for 04-06. Priced at $330. So Im thinking the local shop is quoting me with an '04 part?

I also found a 2 part unit by Flowmaster, part number 2049170, but it also says 04-06. Priced at $250.

People I talk to tell me an '04 wont work, as its a different system.

So what are y'all using as a replacement for an '03? Or will any of those work?

My '03 has the 4.0, and I've got over 300,000 miles on it.
 

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Just a clarification. P0420 is a code that indicates the catalytic converter is not operating efficiently enough. Doesn't necessarily mean it's plugged. You'd know by the lack of engine performance if it was plugged.

I have had good luck in the past using Walker Exhaust direct fit line. They are usually direct bolt up and be of good quality. I looked at 04 for you and they look like they have options. Just spend the extra money and get direct fit and avoid universal. Universal means it's harder to install.
 

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Just a clarification the downstream sensors monitors the pre cat efficiency not the main cat efficiency as they before the main cat


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Discussion Starter · #5 ·
Odds are need to replace mini cats not main cat


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That would be nice! Especially since the '03 seems like an oddball year exhaust wise. A year or two back and its cheaper, a year forward its cheaper, but '03 is double the price!

Currently, it drives mostly fine, til I really give it gas, then it chokes.
 

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Discussion Starter · #6 ·
Just a clarification. P0420 is a code that indicates the catalytic converter is not operating efficiently enough. Doesn't necessarily mean it's plugged. You'd know by the lack of engine performance if it was plugged.

I have had good luck in the past using Walker Exhaust direct fit line. They are usually direct bolt up and be of good quality. I looked at 04 for you and they look like they have options. Just spend the extra money and get direct fit and avoid universal. Universal means it's harder to install.
Right on! I'll take a gander at them.

Looks like Walker on Rock Auto for the pre's (part number 53461), is $338. Bosal is listed as Premium (part number 0793108), and is $275.

I agree, direct fit would be best.
 

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Discussion Starter · #7 ·
These codes started popping up a month ago, what really freaked me out was when the engine light flashed a few times on and off yesterday after laying into the pedal.
 

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The wife’s 04 rubi had same issue and was pretty easy to replace just pre cats with cut and clamp at distal end

The two bolts per pipe at proximal end were no fun as clamp on nuts were badly rusted

The replacement had the bolt flangers inverted which needed longer bolts but as bolt head was not in a recess I could use a flex head ratcheting box wrench on install which was an improvement

The failed minicat had somehow converted most of its guts to a golf ball or little larger wad of material

After removal and before install I ran a shop vac hose to inlet of main cat to remove any precat material that had progressed down to main cat inlet screen




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Discussion Starter · #10 ·
The wife’s 04 rubi had same issue and was pretty easy to replace just pre cats with cut and clamp at distal end

The two bolts per pipe at proximal end were no fun as clamp on nuts were badly rusted

The replacement had the bolt flangers inverted which needed longer bolts but as bolt head was not in a recess I could use a flex head ratcheting box wrench on install which was an improvement

The failed minicat had somehow converted most of its guts to a golf ball or little larger wad of material

After removal and before install I ran a shop vac hose to inlet of main cat to remove any precat material that had progressed down to main cat inlet screen




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Yeah I was a lil worried about the bolts up by the manifold. If I tackled this, I was thinking spraying it with Kroil, then heating it up by running it. What size bolts did you wind up using?

Good idea on the shop vac!
 

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Discussion Starter · #11 ·
Amazon has the Bosal 079-3108 for $314.06
Thanks! But Rockauto has Amazon beat, at $275.

Bosal is the one Im leaning towards.



Seems the single pipe containing all 3 cats was discontinued, and no one carries those anymore.
 

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I had inefficient catalyst codes too. Turned out Bank 2 mini-cat was blown out completely!

Very happy with Flowmaster stainless from Summit Racing $250 for 2 piece set with mini-cats and main cat. Nice welds and smooth mandrel bends! No wrinkles. Photo was when I was lining things up with the manifold. It was a one-person (me) DIY with a jack to hold the first section in place while catching the flange bolts. No adjustments needed. Perfect direct fit!

I added an MBRP stainless cat-back exhaust for another $250.
 

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Discussion Starter · #13 ·
I had inefficient catalyst codes too. Turned out Bank 2 mini-cat was blown out completely!

Very happy with Flowmaster stainless from Summit Racing $250 for 2 piece set with mini-cats and main cat. Nice welds and smooth mandrel bends! No wrinkles. Photo was when I was lining things up with the manifold. It was a one-person (me) DIY with a jack to hold the first section in place while catching the flange bolts. No adjustments needed. Perfect direct fit!

I added an MBRP stainless cat-back exhaust for another $250.
I remember your thread lol, and I was gonna go the Flowmaster route cause of your thread, and the price, but its a 2004-2006 system. I even called Flowmaster, and they said they didnt have it for 2003, and that it was a different system.

Although I think in my extensive search, I "think" I saw somewhere that Jerry said he talked to Blaine, and that they didnt think it mattered. The only difference "might" be the hanger.
 

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Pretty much no differences 03-04 but substantial changes 05-06 vs 03-04

I would check the parts fishe and see if different 03 vs 04




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I remember your thread lol, and I was gonna go the Flowmaster route cause of your thread, and the price, but its a 2004-2006 system. I even called Flowmaster, and they said they didnt have it for 2003, and that it was a different system.

Although I think in my extensive search, I "think" I saw somewhere that Jerry said he talked to Blaine, and that they didnt think it mattered. The only difference "might" be the hanger.
Ooooh yeah... Now, the conversation is coming back to me.

Don't you just love it when the change from year to year is almost unnoticeable, but still different enough to make a difference in whether a part is cheap and available everywhere or is harder to find/higher priced?

Looks like you have a decent option at a not-to-bad price.

You'll see how much your new cats will improve how your engine runs overall.
Should run nice!
 
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Discussion Starter · #16 ·
Well I ordered the Bosal precats, all 4 NGK O2s, and new Autolite XP985 spark plugs.

My nephew and I think we can tackle this. After cutting off the old precat, do I need some kind of coupler to mate the precat to the main cat?
 

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The one I got had a short section that fit over existing pipe in front of main cat and included a clamp

I first made my sazall cut far forward so I had plenty of pipe
Then installed the new pre cat piece loosely so I could see overlap and where I wanted to recut existing pipe that feeds main cat


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