Thread: Codes from deleted cat any worry?

I had researched this before, but I wanted to be sure before I leave anything be. I will be installing a 3" catless downpipe on my 07 l32. Previously, I did not know that the o2 sims don't work on these newer models, and that you can't even tune these computers at all -.- I know I can get one from an 05 to work, but zzp says that not only will my gas gauge read backwards (doesn't matter to me), but also my remote start will no longer work... Seeing as I live up north where a lot of the winter sees as low as -30*C without any wind and -50 or so with, I don't want to lose this feature.

So I guess my only option is to try spark plug defoulers, and I am hearing from pretty much every shop here that they don't work usually. So instead of wasting more money on buying a catted one that likely still will throw a code anyways, until I get headers and do enough to need a tune, I will be likely living with the code. Will the codes associated with running catless affect anything or just have a pretty light? Performance, mpg, any damage, etc?


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I think Overkill solved the gas gauge problem but you would need to email them, lots of people have used foulers with success and its worth trying for a few bucks before laying hundred or so on a tune. I think you will get craptastic MPG because the car has a cat diagnostic which uses more fuel but don't quote me on it im not too sure I just know you get bad gas mileage at least on my dads 01 we did . Why not skip the DP and just do Headers? It would be way more beneficial in the long run for just a little more money.

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Fuel mileage will likely go down, as it see's no cat there.

I'd just chop your factory cat out of the stock downpipe and get it welded in the 3in downpipe. Problem solved and you dont have to spend more money on foulers that likely won't work and trying to get a tune.

Think smarter, not harder.

Headers will be later when I get a bunch of parts together (or ever decide it's worth it to do so). Currently my flex pipe has ripped right open so I found this downpipe for relatively cheap shipped (shipping is costly here). Currently my car throws two codes for the rear o2 and one for the front because of the size of leak in my current downpipe. Right now I am just deleting the codes as they pop up, with y code reader staying beside my seat lol

As for putting in the stock cat, that would be a drastic reduce and I doubt any shop around me would do it. And I've read that the cats that people get on these downpipes allow more through so it is hit or miss wether it'll throw a code anyways. As for my fuel mileage, I'm not seeing much change in mpg compared to before, however I wasn't watching it too hard before. I did however lose some torque I think because of how little back pressure it has. It's pretty much straight out the flex now with very little through the actual exhaust


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So pretty much, I won't see any negative effects if I just delete them as soon as I see it pop up?


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Originally Posted by Daven

So pretty much, I won't see any negative effects if I just delete them as soon as I see it pop up?


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Nope as long as those codes are pending you'll see a decrease in mpg

Buy the right one!^ I made that mistake the cars are finicky about their emissions

I will switch to headers down the road when/if I ever get a cam setup together as well. But considering what all needs to be done to even just tune it, I might either sell this or run it for winters later anyways. Even if I did headers alone, it wouldn't solve the problem that even catted aftermarket systems appearantly are hit and miss wether I'll get the same code anyways. And I'm not spending far more to go back to stock downpipe anyways

I was simply wondering if the codes would have any chance to send the car Into limp mode or etc or if I could run with the codes popping up indefinitely. As I said, I have been deleting them moments after they pop up and haven't yet tried defoulers. But incase those don't work that would be my last scenario


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I use the spark plug foulers before for awhile before I had the codes deleted and I had the cat code pop up maybe once. Ran fine without it. Eventually I had the codes deleted and threw in a cat for other reasons but it's sure worth a try to try the fouler first. It's inexpensive.

Definitely my plan first! Were you able to get two of them in there to space it? I know some cars have clearance issues


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I noticed some places are actually making extended 02 bungs now. You can guy them on Amazon and ZZP even sells them. http://shop.zzperformance.com/store/...-Extender.aspx

Yeah I heard of these too. But it seems like these wouldn't be any different from a DIY option. I don't mind doing the defouler route unless there's any reason these would be set apart as any better?


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Originally Posted by Daven

Yeah I heard of these too. But it seems like these wouldn't be any different from a DIY option. I don't mind doing the defouler route unless there's any reason these would be set apart as any better?


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I tried a single defouler, didn't work. I run an emulator now. Had one of those go bad after just over a year. Got another and have been using it probably 20K miles now. I don't think you will experience any difference in how it runs if the code has set. Somewhere I read that the computer only checks the rear 02 sensor on "every third long trip", which meant every third time you drive for more than half an hour. So even if you chop off a cat today, it may not set the CEL for weeks depending on how you drive.

You can't run those emulators on an 01+ car as the cat diagnostic still runs and you will just end up dumping fuel. http://www.grandprixforums.net/threa...ou-should-know

Originally Posted by Slick2500

You can't run those emulators on an 01+ car as the cat diagnostic still runs and you will just end up dumping fuel. http://www.grandprixforums.net/threa...ou-should-know

Busted! I'm way off, didn't read the car's year. Thanks

Yeah I didn't know that either till I bought my 01.

Originally Posted by Daven

Yeah I heard of these too. But it seems like these wouldn't be any different from a DIY option. I don't mind doing the defouler route unless there's any reason these would be set apart as any better?


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Just somebody trying to capitalize on a easy inexpensive product and mark it up. Spend the 5 mins and do it yourself lol

So this diagnosis makes the engine run really rich to determine if the cat is working? Would this have the potential to damage anything?

And is it always after 30 minutes or is there a way I can prevent it by taking a break now and then when cruising? I like to drive in my spare time, so maybe I could just park every so often and at least turn it off and on to prevent this?


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Just either run without a cat and with the rear 02 in and let the cel come on, it won't hurt anything, or do the non fouler trick.
I've been running my car with the rear 02 code for over a year and my fuel trims are fine.

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