Cat delete, O2 Sensor CEL fix

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12-29-2011, 06:12 PM
pecanflyboy

Cat delete, O2 Sensor CEL fix

Hey everyone!
I've spent a couple of hours reading through threads about how to fix the CEL associated with removing the catylatic coverter. Please don't preach to me about pollution. This is a steet legal, track car and I'm proud of my carbon footprint.

I have an aftermarket header/exhaust system that has the cat deleted. The second O2 sensor has been simply zip tied to the frame as the there is no bung welded into the pipe. I'm currently throwing a code: P0140 - 02 Sensor Circuit No Activity Detected. This code should not have any influence on the tuning of the ECU, as it only monitors the efficiency of the cat.

From what I've read, I have several options but I'm not sure what is best:

1. Weld in a bung and install an O2 sensor spacer or mini-cat spacer. IF this works, it would probably be the most realiable fix as there are no electronics involved. How successful have you drivers been with this fix after removing the cat? Is it worth paying the extra $$ to get the mini-cat? Any recommendations?

2. Various O2 sensor emulators/simulators/eliminators. I've seen everything from DIY circuit boards to semi-professionally produced products. It seems that the big companies get pressured by the EPA not to sell these products. I'm not clear on a couple of things. If I use an O2 simulator, is the old O2 sensor removed and the box wired into it's place? Any luck with the DIY boards? Feedback and recommendations are appreciated.

Jimmy
1996 Miata, 5spd
12-29-2011, 06:36 PM
fwMiata

no, but i have seen the spark plug antifouler method used sucessfully. I have never done it personally to my cars though.
same method, but apply it to the "post cat" secondary sensor.
http://www.esmhome.org/library/o2-se...2nonfouler.pdf

i do run this on my discovery, but it does have a cat, just not OEM (oem is 2 cats, i modified it to 1 cat for both banks) and I didnt want the chance of it throwing a fault.
12-30-2011, 08:32 AM
pecanflyboy

Thanks,
I've seen this method used and discussed in many forums, so it must be affective, and cheap. There are some that advertise a similar device that is a machined spacer and it supposedly a "mini-cat." Thanks for the suggestion.
12-30-2011, 10:23 AM
SirHustlerEsq

I gained a bunch on nothing on my car when I removed the cat aside from some noise. I bet my carbon footprint is bigger than yours, lol.
12-30-2011, 10:48 AM
MiataMike

RAWWRR!!

http://www.poetsforlivingwaters.com/...-footprint.jpg
12-30-2011, 10:55 AM
pecanflyboy

Well, the issue is not whether to remove the cat, or not.........as it is already gone.
12-30-2011, 03:44 PM
OZMDD

Mini cats do work, dptune sells a nice one. Weld a bung on there, very easy. Just did two myself.

Not running a cat is still uncool, no matter how you slice it. Unburned fuel is smelly and polluting. Sack up and buy a $50 race cat. Otherwise, it's just lazy.
12-30-2011, 07:55 PM
pecanflyboy

Quote:

Originally Posted by OZMDD

Not running a cat is still uncool, no matter how you slice it. Unburned fuel is smelly and polluting. Sack up and buy a $50 race cat. Otherwise, it's just lazy.

Dude, I just dumped 100 TONS of burned diesel fuel in the upper atmosphere over the last two days. If there is a carbon footprint hell, I'm sure that a cat on my lil 'ole Miata is not gonna help me.
12-30-2011, 08:09 PM
SirHustlerEsq

Quote:

Originally Posted by OZMDD

Mini cats do work, dptune sells a nice one. Weld a bung on there, very easy. Just did two myself.

Not running a cat is still uncool, no matter how you slice it. Unburned fuel is smelly and polluting. Sack up and buy a $50 race cat. Otherwise, it's just lazy.

I passed an instpection 2-years ago with no cat converter on my 1991.
12-31-2011, 08:55 AM
pecanflyboy

I'm not as concerned with the inspection, as to what is the best solution to keep the CEL light off. O2 Simulator, or spacer for the O2 sensor?
12-31-2011, 10:26 AM
OZMDD

Quote:

Originally Posted by mr brg

I passed an instpection 2-years ago with no cat converter on my 1991.

What are the odds that his car is tuned as well as your 91? I'm not saying you can't make the engine run clean w/o a cat, but 99% of old Miatas on factory ecu's don't.
12-31-2011, 10:43 AM
pecanflyboy

Uuuuuugggghhhhh. Please stay on topic. Passing inspection is not the issue. I can pass inspection with a CEL because I live outside the metromess where we can shoot our dinner, and burn our trash.

I just want the CEL light off for this O2 sensor issue, so that I will pay attention to it if it comes back on.