Removing catalytic converter without getting CEL

[DemoFly]

My Dakota is California compliant, so it has 4 cats and 4 O2 sensors.

My downstream passenger side cat is bad. The sensor is fine and voltage specs out. However during operation it mostly sits at around 0.45v so the cat isn't getting hot enough.

I don't have emission laws where I live, and personally would just like to remove the cat and weld in a pipe with a bung fitting, but I believe it would throw a code still.

Any ideas?

 

[GutsyGecko]

Use a few spark plug washers to move the tip of the o2 sensor towards the edge of the pipe out of the direct stream of gasses. Been doing it like that for years.

 

[DemoFly]

Originally Posted By: GutsyGecko
Use a few spark plug washers to move the tip of the o2 sensor towards the edge of the pipe out of the direct stream of gasses. Been doing it like that for years.

So the upstream sensor would read correct and the downstream would then read correct? (lean after second cat)

 

[bdcardinal]

You can use a spark plug non-fouler, I think the Dorman number is like 42002. If you want to get fancy there are pre-made ones like here: http://vibrantperformance.com/catalog/product_info.php?cPath=1022_1069&products_id=2009

 

[bdcardinal]

Originally Posted By: DemoFly
Originally Posted By: GutsyGecko
Use a few spark plug washers to move the tip of the o2 sensor towards the edge of the pipe out of the direct stream of gasses. Been doing it like that for years.

So the upstream sensor would read correct and the downstream would then read correct? (lean after second cat)



Yup, the rear sensor's only job is to monitor catalyst efficiency, has no effect on air/fuel ratio.

 

[yonyon]

What is the actual problem you're trying to correct? Are you experiencing a loss of power or misfires specifically on one side of the engine? Have you observed lack of intake manifold vaccuum? Unless the cat is "bad" in such a way that it creates excessive restriction there is no advantage to removing it.

If you want to eliminate a cat because it is "bad" only in that it is inefficient and turns on your check engine light, and if you want the light to stay off, you will find the task easier by leaving the bad cat in place.

 

[AandPDan]

Are you positive you have 4 cats? Dakota's, at least '00 and '01 with CA emissions, only have 3. Two upstream (pre-cats) and the downstream. Do you have dual exhaust?

Only the precat's are monitored, not the cat itself.

You have two upstream O2 sensors ahead of the precat and two downstream O2 sensors behind the precat. Removing the cat shouldn't cause any check engine light.

 

[Chris142]

You do know that removing a cat is a federal crime regardles of wether you have emission tests or not.

 

[901Memphis]

Originally Posted By: Chris142
You do know that removing a cat is a federal crime regardles of wether you have emission tests or not.


^California way of thinking

 

[bdcardinal]

Originally Posted By: 901Memphis
Originally Posted By: Chris142
You do know that removing a cat is a federal crime regardles of wether you have emission tests or not.


^California way of thinking


It is actually a Federal law, just some states enforce it. That being said I took the cats off of my 98 Mustang GT and will probably take them off my '14 when I scrape the money together for a Borla ATAK catback.

 

[Roadkingnc]

You can purchase cat sensor eliminators that just plug into the harness and generate the correct reading to keep the light off

 

[Cujet]

Originally Posted By: Chris142
You do know that removing a cat is a federal crime regardles of wether you have emission tests or not.


Federal laws enacted under the so called "commerce clause" do not apply to individuals not involved in commerce. That is the responsibility of the states.

 

[Clevy]

Originally Posted By: DemoFly
My Dakota is California compliant, so it has 4 cats and 4 O2 sensors.

My downstream passenger side cat is bad. The sensor is fine and voltage specs out. However during operation it mostly sits at around 0.45v so the cat isn't getting hot enough.

I don't have emission laws where I live, and personally would just like to remove the cat and weld in a pipe with a bung fitting, but I believe it would throw a code still.

Any ideas?



Buy a tuner and shut off the rear O2 sensors. I've done that with all my mustangs. Running Mac headers to a Mac prochamber without cats.
A speed shop with a dyno can do it for you too

 

[DemoFly]

Well I installed a spark-plug anti-fouler as a spacer and I can't tell if it's fixing the issue or not.

Voltage differences between upstream and downstream have separated like they should be, but now, at a stop, if I rev the engine and let it drop back to idle, the engine will bog and then stall.

 

[bdcardinal]

Originally Posted By: DemoFly
Well I installed a spark-plug anti-fouler as a spacer and I can't tell if it's fixing the issue or not.

Voltage differences between upstream and downstream have separated like they should be, but now, at a stop, if I rev the engine and let it drop back to idle, the engine will bog and then stall.


The anti-fouler trick is only for turning off the CEL. It won't fix an actual problem with the car.

 

[yonyon]

There should be no possible way the anti-fouler (I assume you put it on the downstream O2 sensor) could cause a stalling problem.

 

[901Memphis]

You sure you out it on the right sensor?

 

[DemoFly]

I put it on the downstream sensor, for sure.

I have since removed the anti-fouler and installed a washer about 3mm in thickness (thinking that the spacer moved the sensor away too far from the stream of gasses.)

The downstream sensor consistently reads richer than the upstream sensor. The upstream sensor bounces around but averages 0.3v and the downstream bounces around and averages 0.75v.

This makes me believe the upstream sensor is bad because I don't see how a bad catalytic converter could make the exhaust any richer than upstream gasses.

 

[Thermo1223]

Originally Posted By: 901Memphis
Originally Posted By: Chris142
You do know that removing a cat is a federal crime regardles of wether you have emission tests or not.


^Proper way of thinking


There aren't many things I will say CA is right about but air pollution is one of them.

LA could easily be any other part of the country in due time.