If I cut all 4 cats off of my 04 5.4 ext. will it screw with my computer or make my "check engine" light come on? I want to run TRUE duals. Without cats. Anybody got this set up? Help please...

 

Yes, your not tuned for that, and it's won't be street legal in most states.

 

being street legal isn't really an issue... i just need to know if it'll mess up my truck and wat I need to do to make my computer tuned for it.

 

Yea , good luck with that - Happy Polluting! I hope you get caught

 

x2, but whatever its your truck and your choice.

You will need a custom tune to turn off the CEL. Performance shouldn't gain any with no cats since these trucks have a longer exhaust system than other vehicles, and its a 5,000lb truck, but it will definitely be loud.

 

darren, I noticed that you have your rear cats removed. did that cause any problems to the truck or anything? I may just go with that set up and worry about cutting the front 2 off later.

 

My economy increased 0.1mpg, and my sound level increased about 30%. No engine light because 2004 - 2005 4 cat systems O2 monitor the pre-cats only, not the rears, so the rears will come out without any codes thrown.

The rear converters are what really kill sound and the flow path, pre-cats are pretty much direct flowing as hi-flow converters are. If I was to have the pre-cats removed, I would throw the engine code, and economy would drop.

 

97-03 you can remove the front two cats without any problems

and

04-08 you can remove the rear cats without any problems

As a general rule of thumb as long as you dont mess with anything between the 02 sensors you are golden.

 

You can remove the rears too Patrick - 97-03 without any problems. That's how I ran it -



You just can't run cat-less without a tune on those models..

 

True, But removing the rear converters will in time elluminate a CEL, it has on many members whom have done it, though it depends I suppose, Custom tuning, and those whos rear cats are O2 mounted and the ones that aren't.

 

No it doesn't ? Your still within parameters as long as you don't have a leak.

Where did you get this info ? PO420 & 430 WILL NOT come with this mod and you'll still pass inspection.

It can't leak, you have to weld it together.

If you have data supporting your post , lets see it.

BTW - What do you mean ~ "In Time" ? - Wait , I think I know, are you talking about the failing three consecutive times before the light. 3 drive-cycles. ???

Nah, as long as the system doesn't leak , your good.

 

I do not have any specific data, like I said i've seen in older postings that a couple people have got CELs after the work, I could probably search and find more information, but thats just what I have observed. I dont know from experience because I own a 2004, so I dont know.

 

I run gibson headers with true duals all the way to the back with 4" magnaflow tips on my 2005 5.4. I run one cat on each pipe and flowmaster mufflers with no problems. It has been this way since 8000 mile and my truck has about 50000 on it now. So it goes gibson headers to Cats then flowmaster mufflers true duals all the way back and sounds great.

 

Yea , that's a better set up on these fords with a stock tune.

 

Don't waste your time, they probably had leaks. If done right, it works fine Darren.

You'll even get better mileage.