RobJ25

I'm considering going catless however I'm somewhat confused about the sensors part of doing so.

I heard you can use this "spark plug fouler" trick to get the check engine light off.

My question is, there are 4 "sensors" 2 each side, the o2 sensor and the monitor. Do I need both sensors to keep my MPG from being messed up? I already know the emissions will be screwed up but living in FL im not concerned.

I'd like my car to function "properly" without the cats, and not run like ****.
these are the pipes I was looking at: http://www.jbaheaders.com/detail_mid....asp?id=2809SY

car is a 2004 GTO

Thanks.

Chawlz

I'm not familier with spark plug fouler trick, but I have had several cars without cats, including my current 05 goat. All the cars already had cats removed when I got them except an accord that I gutted it because it was clogged, ran fine after. I have never had issue with car running bad, just turns on light and changes sound of exhaust. The rear o2 sensors only monitor efficiency of the converter. On my 00 z28 I originally used "dummy sensors", didn't actually have rear sensors, just a little box that plugged into the harness and tricked ecu to not turn on light. I later had it retuned and didn't need the dummy sensors. My goat has the light on and runs fine, but I plan on having it retuned eventually.

RobJ25

So if i take my o2 sensors and put them where the monitor sensors would go in my new pipe, i should be good to go?

skidooingit

The front or precat O2 sensors with adjust air fuel ratio and r important to the drivability of your car. The rear o2 sensors or post cat o2s r strictly for emissions in that they monitor cat. Efficiency when u remove the cats. U can remove the rear o2sensors by having them tuned out by software like hp tuners or efi live, or a handheld tuner will also be able to remove or shut of the moniter function of the rear o2s, then ur car will not throw a check engine light. The spark plug fouler trick might work however its not worth messing with in my opinion just have them tuned out. Another option would be having them tuned out via a mailorder tune by someone like frost and u will pick up the hp from the tune as well.

RobJ25

Thanks for the feedback. I learned something new today

skidooingit

No u will throw a check engine light. A frost mail order tune is 150 ish and will be worth it. What other mods u have or going to do?

RobJ25

Well the "spark plug fouler" thing is what i was going to do in reguards to the check engine light. As far as other mods i just have borla mufflers/tips.

adamc45

Go get a dyno tune from a performance shop. U will know the output and they tuned my check engine light out. I couldn't pass inspection if they looked under my car, but half the people around here won't lift it up to inspect it.

thehazz12

That's not going to work. At least not the normal non-foulers... The ones MavMan carries probably would because they take the o2's way out of the exhaust stream, but I don't see the point in paying $50 for those when $200 will get you a tune. However, you have 0 mods so I wouldn't waste my time or money on a tune until you at least have some bolt-ons.
How long until you need the car to pass emissions next? If not for a while...rip the cats out, replace them, ignore the CEL, get some other bolt-ons, then get a tune.
FWIW, mine is longtubes, catless, catback, "CAI", SLP 85mm MAF and for almost 2 years untuned. It throws DTC's, but drivability is not affected.

Dr.Goat

What I did is I took two open end bolts and filled them with steal wool, it allows for a good mixture of full and air so it doesn't over compensate mixtures. I haven't had a single check engine light for months now!! Worked great, and you only have to do that on your secondary o2's bc the first set was before your cats anyway. I don't know if that answers your question fully enough, but I will say it worked like a charm for me, I though about doing a DIY

africangoat

I am thinking about going catless as well even though I am in va. I have jba shorties and will be using jba catless mids. I hope I can tolerate the smell

thehazz12

If you have a proper tune on the car so it's not pig rich and no leaks in the exhaust, you shouldn't have any issue with smell.

svede1212

iTrader: (3)

IMHO catless smells much better than any catted car. They smell like rotten eggs.

Dr.Goat

Ya, if you do get a tune then you won't have to worry about it, they'll just tune it out, what I wrote above was temporary before I had a tune.

SJFGTO

Every time I walk behind by GTO it smells like its 1970 all over again.

markpetersonii

iTrader: (1)

I have a catless 04.

When I installed the mids, O2 extensions were just put on and I have no check engine light.

thehazz12

Give it time. You "should". With no cats and a tune still incorporating the rear 02's, you should definitely get a CEL sooner or later. For whatever reason, mine goes away at times or after I clear the code sometimes it'll take a pretty long time to come back on. However, I really don't drive mine very often so that could play a part.

markpetersonii

iTrader: (1)

Well, it's been a month and nothing.