i was thinking about chopping off my last cat but i wanted to know if it was worth it or if it makes things worse. i tried searching the topic and couldn't find anything useful.So i guess i'm just asking if it is a good or bad mod soundwise and performance wise. will it increase mileage or decrease mileage? thanks for any help. other suggestions welcome..

 

On a 2003 you'll get a permanent CEL. The cat is monitored for efficiency by an oxygen sensor downstream of it. If you whack it, you'll get a CEL and it will not pass emission testing if your state cares.

Besides -- the cats on 2001+ are high flow from the factory. It won't do much for you anyway.

 

you wont get a CEL... the last CAT is after the last o2 sensor in 01-03 4.0s not sure about 3.0... 04+ 4.0L do not have that 4th CAT

but you wont get any improvements but more sound

 

Okay, didn't know that. I believe my last CAT is monitored. Mines a 2002 3.0.

 

Well i know a few people that have 01-03 and removed that last cat... plus i am only running 2 cats here in a few weeks. and still utilizing the stock o2 sensors, i should not have a CEL when I am done... but then again i said "should not" LOL

my new ones are high flow aftermarket 6000lb catalytic converters which actually should clean the air better than stock...

 

so it's pretty much pointless then

 

not exactly, you will gain sound and could gain a little performance. plus the scrap yards are getting almost 100 bucks for cats nowadays....

 

true. i don't really care for it being louder though i just wanted to know if it helped enough in performance to help my mileage.

 

It will free up a little flow and make it sound better/louder.

You should not get a CEL.

 

Correct. As long as there's no O2 sensor after the cat. To be absolutely sure, I'd check it before you cut, lol...

 

So if you take one the 4th cat off does it still pass emissons is the only question....hmmm

 

If your State has an emissions test or a State inspection program that checks for related equipment they can still fail you for not having the device in place even if your tail pipe emissions are within specs.

 

i have both of my cats off and no cel. i was concerned so i scanned it at work with the mastertech and it is still within specs

 

Thats why its good to have an emissions and safey inspection license...haha i can look right past it. And I can also inspect my truck and it would on't cost me the stickers.

 

Thats really not something to brag about. If you have a license through your state commission, you are under a binding contract with them, if you get caught passing vehicles(not including your own) that are out of specs, you can be fined very heavily and around here, our inspectors can not only lose their inspection license, be fined up to but not limited to 10,000 dollars, they can lose their drivers license, and face jail time... The inspection license is nothing to take lightly! Be careful who you gloat around.

 

Ya know what's crazy? I don't have any catalytic converters, nor any 02 sensors (of the 4 that SHOULD be there).

I don't have a Check Engine Light!!!

 

does your cel light work? lol. kinda hard to believe its even running without the o2s

 

I've got a CEL on. It said something about too much exhaust flow or something. idk. I'll get it scanned again when I can get it driving again.

Brenton

 

my 5.0 f150 runs without the 02's but the cel flashes and the computer is in open loop

 

probably an egr monitor code. means either your egr valve is stuck open, your egr control solenoid is bad, or your dpfe is bad... replace all three..... be done with it.

 

why do you have the o2s taken out?

 

I wasn't saying i do that to...i was just saying if i took my cat off. I can pass my Safety side of the test Emissions theres no way to cheat it. It plugs into your truck and reads the readings and says if it passes or not. The biggest thing to worry about would be the tailpipe test.

 

the safety part does fail if you remove a cat. whether the obd2 test passes or not, everything that came on the vehicle(emissions wise) MUST still be there in order for it to pass the safety portion. Including all cats, unleaded gas restrictor, evap canister, and whatever else it came with from the factory. Even the o2 sensors HAVE to be there in order for it to correctly pass an inspection.

 

I did it and could not stand it. I gutted both and drove with it like that for 2months. didnt really notice any change except slower take offs.

It was very loud and it sounds stupid because your really not going as fast as it sounds, if that makes sence. Going up a hill is hell and it sounds like your truck is going to explode.

I just finnally found a replacement cat at a junkyard that would sell me one. Now I have the cats with a $20 autozone cherrybomb and it sound great. 3.0v6

 

you did something totally different than what we are talking about. the 4.0l trucks have two preheater cats and two 3 way cats. the very last cat has no o2 monitor, so you can delete it without a cel and gain some sound with an aftermarket exhaust system