Cat Delete and DIY O2 Simulator
 

About two months ago I got a CEL for Low Catalytic Efficiency. I have been waiting for this to happen, it gave me a reason for cutting the cat. out. I have read on this website many times about aftermarket cats failing and having to pay some serious money for a OEM cat. Well I'd rather buy a new gun than pay $500+ for a catalytic converter for some tree hugger none sense. Also if you are going to talk about it being against the law for me to cut the cat out let me stop you right there. As long as it is safe to drive, I will configure my vehicle however I want. Now there are people who like to say the 3.4l likes some back pressure and it actually decreases low end power. Well until you show me a dyno test I do not believe you. You almost sound like those people who think the Deck Plate mod isn't worth it. If you increase air intake and better exhaust flow, you increase power.


I have a '99 4runner limited. The Deck plate mod and ISR delete are the only engine mods I have completed along with regular maintenance. I also replaced the stock exhaust with a flowmaster years ago.

FOR THE ACTUAL WORK:

1)There are two sensors, one before the cat and one after. Unplug the sensors. I have the cali emission exhaust so I have two cats. Also remove the rubber links that connects to the exhaust and frame support, get some WD40 in their.

2)The section of exhaust pipe with the cats and sensors can be unbolted. Three bolts hold it in place to the exhaust manifold, and two bolts hold it place about half way down the car. Separating this section of pipe from the section of pipe with the muffler. I had to heat up the bolts to remove them.

3)I cut the pipe in the middle, this allowed me to remove the pipe around the frame cross members.

4)Now that I had the pipe out of the car I removed the sensors, each one had two nuts hold it in place.

5)I cut the pipe right before and after the cats

6) $16 of exhaust pipe and couplings from O'Reillys, I welded the straight pipe in place of the cats.

7)Remember those rubber links? The support bracket on the old exhaust, I grinded the weld off removing it from the pipe and then welded it on the new straight pipe.

***O2 SENSOR SIMULATOR***
I ordered the following from amazon:

https://www.amazon.com/gp/product/B0...?ie=UTF8&psc=1

https://www.amazon.com/gp/product/B0...?ie=UTF8&psc=1

8)I took the rear O2 sensor and carefully cut the protective wire cover. I cut the blue and white wire and soldered the resistor and capacitor just like the diagram I attached below. A lot of heat shrink, zip ties, and a good amount electrical tape you have your self an O2 sensor for $11.

9)Reinstalled the sensors, plugged them back in. Reinstalled the rubber connector to the exhaust support I relocated.


Two months now and I have no CEL. I can definitely tell the exhaust flow is better. I have not had a chance to do a MPG test because I have been driving like a mad man lately. BUT so far no adverse effects. If anything changes I will post here.

Good timing on this - I just cut out my double catalytic converters to increase flow from the Doug Thorley headers straight through to the Borla Pro-XS muffler... I haven't taken it for a cruise yet and am wondering if my Spark Plug Fouler is going to offset the O2 sensor enough to fake out the signal to the ECU.

If not, I guess I'll be doing this! ha!

Only reason I would go with an aftermarket cat is to use for a silencer. These things on a flowmaster get pretty obnoxious without a cat quieting it down.

Otherwise very nice writeup.

I don't specifically disagree with you about the 'against the law' part, but I'm assuming you checked your state inspection requirements.
Safe or not, in some states, you need a cat if your vehicle is a within certain age range, or they'll fail you outright. Arguing with the inspector over 'treehugger nonsense' won't do you any good.
This also will make it harder to sell your vehicle (if you plan on keeping forever, then nevermind) and you may need to reinstall BOTH cats if you move out of state.

Here in Texas you need a cat if you are 25 years or younger. I chopped the clogged cat out of my 34 year old Wagoneer a few years ago.

Agreed with JayRolla though: nice writeup.

I live in South Carolina. I had never heard of emission tests before I started reading posts on this website!:bounce:

I love not having inspections or emission tests in our county.

We used to run e85 to pass older cars. Worked everytime.

Sounds great!

Hello. I have just a couple of questions concerning this mod.
If the cat is bad and being deleted, and you modify the rear 0-2, do you need to put it back in the pipe? I'm thinking you could just put in a straight pipe and tape/tie up the 0-2 to the top of the fame or something.

Also, let's say you delete the cat. Does this 0-2 mod need to be done before the cat is deleted, or can you drive a short distance after the cat is gone, then do this mod?

A friend is letting me use his garage and welder and just wanted to know if I could wait to get home after the pipe work is done to mod the 0-2.

Thanks

Don't forgot to sell your old cats to the scrap yard, they are worth at least $100 each .

I may be doing this, I keep getting a P0420 code rearing it's ugly head.

Great Write up
 

I live in N.Y. and we have Emissions test annually over here, my truck is 20 years old with 280k on the dash, she runs but falling apart lol and I don't want to put a $1000 into it.

I tried this cat delete and O2 simulator, I passed my emissions test this morning.

Great Write up.

Thank you

Looks to be the $5 RadioShack O2 simulator. Even has the diagram I drew in MS Paint several years ago, lol.

http://www.toyota-4runner.org/3rd-ge...ator-%245.html


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Did this on mine but am now getting a p0141. Did it exactly as this poster has it pictured. Suggestions. I have a 2000 3.4 of course. The front cat is still intact, the secondary housing is in place but gutted. It throws the code as soon as I start it. It will run fine until it comes up to temp and then starts surging under consistent throttle application. Any help would be appreciated.

why do folks what to FUKK UP the air without a cat???