Cat Question

Blue02 · Post by **Blue02** » Sat Sep 19, 2009 10:43 pm

So im thinking of going with no cat when i get my MLH so ive unplugged the current cat to see how the car would act is this alright to do? Just making sure.
thanks in advance

cbjones26 · Post by **cbjones26** » Sat Sep 19, 2009 10:46 pm

unplugged as in u gutted it or took it off? either way u will notice a lil more pep in ur car, i know i did when i gutted mine last year, just get a spark plug non fouler and do the lil trick to make the computer think there is a cat! there is a post on here about it...

here it is

viewtopic.php?t=1025&highlight=spark+plug+non+fouler

ZeroChad · Post by **ZeroChad** » Sat Sep 19, 2009 11:12 pm

I think he meant unplugging the downstream 02. I've been running w/o one for about 6months now. The computer will throw a code now and then, but there are no ill effects aside from emissions.

Donkeypuncher · Post by **Donkeypuncher** » Sun Sep 20, 2009 4:08 am

The downstream O2 sensor has no effect on engine performance, it's only there to make sure the cat is working correctly. The upstream is the one that messes with the a/f ratio and fuel trim.

If you don't have emissions testing where you live, you'll be fine without the downstream sensor. The spark plug fouler is more to remove the annoying check engine light.

Blue02 · Post by **Blue02** » Sun Sep 20, 2009 10:04 am

thanks everyone for the help and CBjones your a badass for digging that up for me lol

Post by **occasional demons** » Sun Sep 20, 2009 11:05 am

Donkeypuncher wrote:The downstream O2 sensor has no effect on engine performance, it's only there to make sure the cat is working correctly. The upstream is the one that messes with the a/f ratio and fuel trim.

If you don't have emissions testing where you live, you'll be fine without the downstream sensor. The spark plug fouler is more to remove the annoying check engine light.

The down stream actually does have input for long term fuel trim. The upstream is more for what is happening at the moment. But if you are resetting the PCM fairly often for w/e reason, then it really doesn't matter. Either way it will still run fine. And the fouler does not have a 100% success rate.

Donkeypuncher · Post by **Donkeypuncher** » Mon Sep 21, 2009 3:28 am

You caught me on that one, I didn't even think about the long term fuel trim. I've heard mixed reports about the fouler trick, seems to be a hit or miss kind of thing.

If you can find one anymore, the O2 simulators are the best option. Last I heard it's forbidden to sell online, kind of like bongs.

2001rt32 · Post by **2001rt32** » Mon Sep 21, 2009 5:11 am

the nonfouler mod worked for me on my r/t i have had no problems. if im not mistaken with a check engine light the computer sets its self into limp mode, im not positive but before i did the nonfouler mod i had the cel for the o2 and i noticed horrible gas milage.

Post by **occasional demons** » Mon Sep 21, 2009 8:22 am

My Jeep got bad (worse) mileage also when the downstream failed. But others claim it doesn't seem to affect their mileage. But then, it may depend on driving habits. If driven agressivly, I doubt the downstream would have much impact.