Cat options...

M

MichiganMan

Test Drive
Location
Michigan
The trusty 2004 SE/SC with 141K on the clock has presented me with a conundrum. It is throwing a P0420 code, catalyst inefficiency on bank one. Took it to the dealership today and they have confirmed that the O2 sensors are working correctly, so the cat itself is the source of the code. Having the dealer replace it is not an option as they want $1100 for the job, and almost $700 just for the part. Not in this century....

A local exhaust shop has told me that they can replace it with a "universal" cat for about $250. Probably doable, but am I borrowing trouble going this route?

Third option would be to replace it myself (Magnaflow has bolt in number for $219) but the ones I've seen are listed as excluding the supercharged model. I can't see as how the exhaust is any different on the S/C over the normal V6 but maybe I'm missing something.

Finally, I'm tempted to just eliminate it altogether but I'd need to spoof the O2 sensors to do that and I'm not sure how to go about that operation.

Any other ideas or advice?
 
robcarync

robcarync

Sliders
Location
Raleigh, NC
From what I understand, you probably have 4 cats. 1 on each manifold, and 1 downstream from each manifold. The oxygen sensor is between the two cats, so if the code is being generated, it must be from the one on your manifold, and not the down stream ones. Since there is no sensor after the last cats, you could chop those 2 out with no problem, and get no codes. The ones in the manifold will trigger the code.

The big importance of that detail is that the local exhaust shop probably doesn't know that. It isn't something you can chop out and weld up a replacement, since it is integrated into the manifold. I have seen that the cat is bolt on to the manifold, or it may be permanently attached, so you have to replace the entire manifold (why they cost so much from dealership).

So, that gets us to your options:

1) Replace just the one manifold with cat and be done with it

2) Get some long tube headers for ~500 bucks, and replace both manifolds, eliminating the upstream cats. note that replacing the headers can be tough, and it is a bit easier if you have a body lift. If you don't, get ready for a headache. You would also need to spoof the o2 sensors, which is a simple bolt on device that spaces the sensor out of the exhaust stream so it reads fresher air. About 40 bucks. 4x4parts.com. This option is cool, but it is expensive, and has possible legal issues depending on your state and vehicle inspections. This also opens the door for more mods...custom exhaust all the way through...why the heck not? Oh yeah, you end up spending more money :)

3) Spoof the O2 sensor on the stock manifold. At least you don't have a light on your dash, but you won't be fixing the problem.
 
M

MichiganMan

Test Drive
Location
Michigan
No inspections here... :) From what I've read, if the cat loses just 5% efficiency it is enough to set off the sensor. The folks at the dealership did say that the cat is not plugged at all, still flowing correctly, so I'd rather not replace a part that is likely doing most of its job.

What genius came up with the integrated manifold/cat combo? Sometimes I wonder what the heck these "engineers" were thinking...
 
T

TJTJ

Skid Plates
Founding Member
Location
NJ
MichiganMan said:
No inspections here... :) From what I've read, if the cat loses just 5% efficiency it is enough to set off the sensor. The folks at the dealership did say that the cat is not plugged at all, still flowing correctly, so I'd rather not replace a part that is likely doing most of its job.

What genius came up with the integrated manifold/cat combo? Sometimes I wonder what the heck these "engineers" were thinking...
Click to expand...

The usual...a combo part is cheaper to make and inventory than separate parts.


The second set are ONLY needed for CA emissions, so if the truck is not going up for sale one day in sunny CA, you will never need the second set.
 
M

MichiganMan

Test Drive
Location
Michigan
The truck will be driven until it dies. I think I'm going to try the O2 spacer and see what happens. For $30 or 40 it's worth a shot over spending hundreds on a new cat.
 
robcarync

robcarync

Sliders
Location
Raleigh, NC
you need a check engine light eliminator. It is a spark plug non-fouler...which fits the threads of the oxygen sensor. You just install the non-fouler (think of a spacer) into the headers bung for the O2 sensor, and install the O2 sensor into the spacer. It just keeps the sensor probe out of the exhaust stream so it monitors fresher air. it makes the computer "think" the exhaust is cleaner than it is.
 
M

MichiganMan

Test Drive
Location
Michigan
robcarync said:
you need a check engine light eliminator. It is a spark plug non-fouler...which fits the threads of the oxygen sensor. You just install the non-fouler (think of a spacer) into the headers bung for the O2 sensor, and install the O2 sensor into the spacer. It just keeps the sensor probe out of the exhaust stream so it monitors fresher air. it makes the computer "think" the exhaust is cleaner than it is.
Click to expand...

Yep, I'm going to order one tonight, I think. Looks like it might be "fun" getting the old one out - yet another reason I need a lift in my garage!
 
KChurch86

KChurch86

Banned
Founding Member
Location
Western Massachusetts
I went through this recently enough. Here's what I did:

DT long tube headers, 4 new NGK O2 sensors, (if your sensors tested OK, skip those), OE-style bolt-in secondary cats, and a pair of THESE (<-- link) CEL eliminators. The straight style eliminators don't have jamb nuts on them, and I found they kept loosening (incredibly aggravating). The 90* ones have a jamb nut to ensure they don't loosen from the bung on the cat. Also, I went with Eastern Industries catalytic converters from RockAuto, though I also considered the Magnaflows, just didn't have the extra cash to burn.

The CEL eliminators need to go on the 2nd set of O2 sensors, not the first. Basically, the first set of sensors (in the headers) will be reading completely un-cleaned, pure exhaust, though the computer still thinks the sensors are reading exhaust that has gone through the first cats (which are eliminated with the headers). The reading taken by the 2nd set of sensors will ALSO be un-cleaned exhaust, since the O2 sensors install UPSTREAM of the cat, so you need to install the CEL eliminators on them so that the 2nd pair of sensors reads cleaner than the 1st pair.

As far as job difficulty, removing the factory manifolds/primary cats is a bear. It's easier with a BL, but completely doable without (I don't have one, and still got it done). Removing the secondary cats isn't as bad, but again, easier with a BL. I needed to cut the old passenger-side cat in half to remove it, and I had to completely remove the transmission/transfer case cross member to install the new. Removing the front drive shaft also makes it a ton easier to get to the driver's side.
 
KChurch86

KChurch86

Banned
Founding Member
Location
Western Massachusetts
It should also be noted that because the 2nd set of O2 sensors install in front of the rear catalytic converters, you COULD just install the DT headers, then have a pair of pipes made that bold up to the headers and include O2 sensor bungs. Then you wouldn't have ANY converters, and as long as you install the CEL eliminators on the 2nd sensors, you wouldn't have a light either, and you'd have the most free-flowing exhaust you could ask for; and no more cats to go bad.

I would have liked to do this, but in Massachusetts, there's a visual inspection and if the inspector sees that there aren't cats, the truck fails. You said there's no inspection where you are, so if that's the case...completely eliminating all 4 converters IS an option for you. Though, it'll be loud, and I'm not sure what it would mean for your MPG either. I'm also not sure if you're willing/able to pony up for that much custom exhaust work (I know I'm not).
 
M

MichiganMan

Test Drive
Location
Michigan
KChurch86 said:
It should also be noted that because the 2nd set of O2 sensors install in front of the rear catalytic converters, you COULD just install the DT headers, then have a pair of pipes made that bold up to the headers and include O2 sensor bungs. Then you wouldn't have ANY converters, and as long as you install the CEL eliminators on the 2nd sensors, you wouldn't have a light either, and you'd have the most free-flowing exhaust you could ask for; and no more cats to go bad.

I would have liked to do this, but in Massachusetts, there's a visual inspection and if the inspector sees that there aren't cats, the truck fails. You said there's no inspection where you are, so if that's the case...completely eliminating all 4 converters IS an option for you. Though, it'll be loud, and I'm not sure what it would mean for your MPG either. I'm also not sure if you're willing/able to pony up for that much custom exhaust work (I know I'm not).
Click to expand...

I have given that some thought, but for me right now the cheapest fix is the only option. In a year things will be significantly better for me in terms of disposable income but until then I'm going to get the angled spacer and see if that fixes the issue.
 
Timrich

Timrich

Super Duper Moderator
Founding Member
Location
Central FL
I prefer an orange tabby...
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