5.3 cat delete

[Jackrichardson13]

I have a 2005 5.3. I have recently been getting the code that my cat is going bad. I could either take them off and bypass the o2 sensors or replace the cat witch would cost more money. I am trying to maximize my fuel economy. I am running a 2.5 inch lift with 33 a/t. I am currently getting 13. I don't have a cold air intake or programmer.

[anumber1]

Could be the o2 sensor after the cat is bad.

 

If you are dead set on removing the cats, your are gonna have the light on anyway unless you get a custom tune.

 

If the truck is your driver, not just a mud toy, fix it and keep the cats.

 

More than likely, all 4 o2 sensors could be tired/lazy.

 

Fuel economy? 33" tires and a lift?

 

Funny stuff...

Edited August 11, 2016 by anumber1

[Jackrichardson13]

Could be the o2 sensor after the cat is bad.

If you are dead set on removing the cats, your are gonna have the light on anyway unless you get a custom tune.

If the truck is your driver, not just a mud toy, fix it and keep the cats.

More than likely, all 4 o2 sensors could be tired/lazy.

Fuel economy? 33" tires and a lift?

Funny stuff...

To replace all four o2 sensors it would be about 400$.

[anumber1]

Looks a lot closer to $200 for all 4 sensors.

 

And that would be buying the most expensive parts at Rock Auto

 

https://www.rockauto.com/en/catalog/chevrolet,2005,silverado+1500,5.3l+v8,1431121,emission,oxygen+(o2)+sensor,5132

 

You mentioned you were all about the fuel economy.

 

Nice, fast, fresh o2 sensors are high on the list of making your truck run as good as it can. That would go much farther than removing your catalytic converter and continuing to run your ride in a poor state of tune.

 

Regardless of whether or not you decide to remove your emissions equipment or not, getting your truck to run to perfection is the best way to ease the pain of low miles per gallon (or turn your 33"s through the bogs or across the desert).

 

While you are at it, a nice, clean MAF sensor is pretty important also...

 

It's not like it's 1981 anymore. The cats on your truck flow pretty good, rarely go bad unless abused and with a stock motor, you will not realize much in performance gains pulling them.

 

Have you been running your truck with a bad misfire for a while? Do you go through a lot of oil? If so, then the cat may really be dead.

Edited August 11, 2016 by anumber1

[onecrazyfoo4u]

Do new O2 sensors improve mileage? How often do they go bad? I'm sure mine are originals, 11 years old and 140k miles...

[anumber1]

Do new O2 sensors improve mileage? How often do they go bad? I'm sure mine are originals, 11 years old and 140k miles...

O2 sensors definitely have a finite lifespan.

 

Even if they "work" enough to not throw a code, they get "lazy" with age and miles.

 

Typically, you can back probe them to see how fast/well they are cycling (measuring in milivolts).

 

So, yes, in short, you can improve mileage if you have slow/lazy sensors.

 

I treat em like tune up parts. Change plugs, change at least the upstream o2 sensors.

[rdnkcpa]

Also, you need to troubleshoot what made the cat go bad. Most likely with the loss in fuel economy, understanding you have 33's and a lift, your computer is dumping more fuel in to compensate for some type of lean condition. I would first check for a vacuum leak. Plug a scan tool in and see what the fuel trims are.

 

If your cats are in fact bad, they are getting cheaper. I just bought one for my son's Monte Carlo for $165 off of Amazon.

 

Second if this is your DD and you want better fuel economy, return it to near as stock as possible. Or, park it and get something better on fuel. I wonder if over on the Prius forums they have people wondering how to increase the payload or towing capacity of their cars.....

 

I parked my Silverado, bought a Chevy Cruze Turbo Diesel for commuting. 42-46MPG on the highway.

[rdnkcpa]

And, I forgot to mention, I replaced all four O2 sensor's on my pickup earlier this summer.

 

I got all four sensors from Amazon for $144.24. AC-Delco Part # 213-1702.

[WilliamBos]

Is their a special socket for O2 sensors?

 

Removing cats will not improve mpg, it could get worse with no O2 sensors. The GM cats have been highflow since they Vortec'd back in 1996.

[anumber1]

Is their a special socket for O2 sensors?

 

Removing cats will not improve mpg, it could get worse with no O2 sensors. The GM cats have been highflow since they Vortec'd back in 1996.

 

Yep.

 

This is a cheap example. Probably fine for occasional use. I have a K/D version of this tool and a 3/8 drive, "crowfoot" version.

 

http://www.harborfreight.com/78-in-Oxygen-Sensor-Socket-69022.html

 

 

 

I really only use the "special" tool to install a new sensor. I clip the wires on the the sensor to be removed and use a standard deep well socket or box end wrench most of the time.

[bryanrey2324]

On 8/11/2016 at 11:56 AM, anumber1 said:

hey i have a 03 5.3 chevy silverado and i want to do a cat delete and replace with headers which headers would be best for it to sound loud?

 

 

[shakenfake]

Literally any headers will make it sound loud without cats.

[L Simpson]

Technically, if you do not have converters, present on your vehicle that is less than twenty five years old, that will fail inspection. 

More and more places are going to emissions testing also. The emission testing is tied in with the state's computer and they will know who does and who does not passed emissions test.

Depending on if You are ever stopped for a DOT inspection on the road, You could receive a fine for the catalytic converter removal.

 

[Kelly88guillory]

I have an 09 Silverado 1500 with a 5.3, has anyone gutted or removed catalytic converters? How’d it run afterwards? What did you do to avoid the check engine light? 

[asilverblazer]

On 2/15/2026 at 12:29 PM, Kelly88guillory said:

I have an 09 Silverado 1500 with a 5.3, has anyone gutted or removed catalytic converters? How’d it run afterwards? What did you do to avoid the check engine light? 

Re-read the 10-year-old thread. 

It will run the same.

You will have to get a custom tune to solve the check engine light.