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Registered
2005 Outback 2.5 N/A
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66 Posts
Discussion Starter · #1 ·
I took my car to a muffler shop to get a couple spots on my exhaust pipe welded, and the tech ended up removing all of the heat shields from the car. I've gotten code p420 (catalytic converter under efficiency) a few times since. I was thinking it was possible that the cat's aren't heating up fast enough and are throwing the code for that reason. does that make sense? Should I try putting some exhaust wrap on the pipes/cat's?
 

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Registered
05 Outback, 15 WRX
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46 Posts
Yes from what I read on the p0420 diagnosis thread the heat shields are very important in keeping them at operating temp.

See if you can go back and get the heat shields and bolts. If they don't have it have them order you new ones. If they laugh then order them yourself.
 

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On the Super Mod Squad
2002 3.0 VDC Wag + 2018 2.5 Leg Ltd
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26,843 Posts
"all" ?

chucking the one(s) over the muffler(s) is one thing,...typically done. (the thing on the muffler might keep some dust / mud off it,...or on it).

chucking the one(s) over the mid pipe, "might" let some extra heat soak up into the car.

chucking the one(s) over the cats is just plain stupid. as it does keep the heat in the cat(s) to make them cook at the right rate, and keep the heat out of the car. (I would think that would be a procedural error at a muffler shop).

does your exhaust smell a bit worse now? like when you first start up the car cold,....and it just stays that way even though the engine and exhaust are hot?
 

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Registered
2005 Outback 2.5 N/A
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66 Posts
Discussion Starter · #4 ·
The heat shields are long gone. Yes, all of them. I thought he was just removing the ones between the cat's and the engine but he took them all off. I think using exhaust wrap is the way to go since the stuff is pretty cheap. I haven't noticed any change in the way the exhaust smells.
 

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Registered
2005 Outback 2.5 N/A
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66 Posts
Discussion Starter · #5 ·
is it a bad idea to wrap the cat? i don't want it to get too hot, so i'm thinking I will wrap all of the exhaust pipes but not the catalytic converters.
 

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On the Super Mod Squad
2002 3.0 VDC Wag + 2018 2.5 Leg Ltd
Joined
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26,843 Posts
p0420 is a mild nag code,

how many miles on this?

I am on my 2nd replacement rear o2 sensor on my 2002 2.5 N/A car. (one at 65,000 miles, and another around 100,000).

bought denso branded ones off rockauto / amazon for around $70.

such things as those sensors, do get old / dirty . so if it starts to appear more often,...and you get tired of canceling it, it is a good place to start vs. more expensive things on the list to fiddle with / diagnose.

however: as its a 2005,...make sure you have the o2 sensors for california/NY or federal emissions.

and ....some here suggest you can get a brand new cat for nothing. (I forget at this minute which cars in the 2005-2009 have forever replacement on a cat).
 

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Registered
2005 Outback 2.5 N/A
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66 Posts
Discussion Starter · #7 ·
105,000 miles. It's still rolling with the original o2 sensors. free cats? I'll have to try searching for some info on that
 

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Master Caster
2005 XT, Mildly Modified...2006 XT Limited, Highly Modifed
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16,221 Posts
1st off all wrap is NOT created equal. The cheap sh*t on Amazon is just that...cheap.

Get some good high quality wrap and you can wrap everything as far as the exhaust system goes. The problem with wrap is, it soaks up dirt and debris and accelerates corrosion.

If you wrap, it would be in your best interest to remove it and rewrap one a year or so...
 

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On the Super Mod Squad
2002 3.0 VDC Wag + 2018 2.5 Leg Ltd
Joined
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26,843 Posts
I was just looking at the price on those shields new OEM online dealer, $18-$37 each depending upon type,...which is not that bad vs. who much they "could" cost.

rock auto does not sell any aftermarket.:frown2: (that I can find??)

read people here DIY installing them / quieting them with bailing wire.
 

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Registered
2005 OBXT Ltd Obsidian Black 5MT
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1,080 Posts
1st off all wrap is NOT created equal. The cheap sh*t on Amazon is just that...cheap.

Get some good high quality wrap and you can wrap everything as far as the exhaust system goes. The problem with wrap is, it soaks up dirt and debris and accelerates corrosion.

If you wrap, it would be in your best interest to remove it and rewrap one a year or so...
This.

I used some of the cheap fiberglass stuff from Amazon. It's terrible.

First off, it's fiberglass, so even handling it to put on your exhaust is a pain because the pieces go everywhere. Even if you soak the wrap with water first, it's difficult to keep it from making a mess.

Second, once the wrap has been on the car for a short while (weeks or merely months), it turns brittle and starts breaking apart.

I wrapped the entire exhaust header on mine with the fiberglass and regretted it immediately.

This was the wrap after being on my header for only about 4 months. It broke apart in chunks.







And of course it left bits of fiberglass everwhere. I was itchy for days after taking it off.

I had a small bit of titanium wrap on the uppipe that came with it, and it's still like new.



I've bought titanium wrap to redo the header, but that's another project.



That's about $100 worth of wrap. I hope it's enough.

What's worse is that I didn't get the titanium wrap oredered in time and had to re-wrap my header in the same cheap fiberglass because it's all I had on hand. So I've got to do it all over again.

On the heat shield rattle front: I found several rocks in the heat shield over my stock cat. They rattled exactly at 2,200 rpm. Drove me crazy until I found it.



But now I've got an aftermarket pipe and it doesn't have any heat shields at all. I had the heat shield that goes above the exhaust hit with a piece of snow and it started grinding on the driveshaft. Had to remove it as well.
 

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Registered
09 Legacy GT, 08 Legacy 2.5i, 09 Outback 2.5i
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170 Posts
Heat Shields

I removed all the cat heat shields from my 08 Legacy 2.5i several months ago. Both on the manifold and the 2nd cat. Solved the rattling issue at the time. No codes, no problems at all. The consensus on several posts on legacygt forums was that removing the heat shields is not a problem and is not uncommon to do.
 

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Registered
1999 30th Anniversary Legacy Outback DOHC 2.5L 4EAT, 2008 Impreza WRX 2.5L 5MT, 2008 Impreza Wagon 2.5L 4EAT
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1,224 Posts
Most of the heat shields on my '99 OBW and '03 Forester have been removed. No P0420 code for me
 
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