Convertor question
 

Will the 5.4 function properly if the cat was cut off? I don't want to have a bunch of idiot lights come on with a constant ding, ding.

Service engine soon lite will be on all the time with the cat removed.

Not if you take the bulb out . . . . .:)

Doesn't Michigan have an emmisions inspection?

Took my cat off and actually got a bump in my MPG and I'm glad to say that no check engine light has came on. The light is still fuctional as well if anyone is wandering.

That will only work on models without the "after-cat O2 sensor". The ones with will throw a code.

Good point, I forgot to mention that. I think the after cat models began in 05' if I remember reading that right. I hope someone else on here with much more knowledge on Superduty's will set me straight if I'm wrong.

There is no emissions inspection in Michigan.

Even if there were, you could just gut it and put it back in.8D

I picked up .5-.6mpg after removing the cat and replacing the stock muffler.

my 99 5.4 has an after cat o2 sensor. im not sure if any models did not have an after cat o2 sensor

my 03 has been fine for the last 5k no cat, custom y pipe and
a flowmaster 40 series. i didnt have an after cat 02 though.

I ordered a set of Dynomax duals for it and thought I might rip the cat off while I'm under there. I remember my dad gutted the convertor on his 78 LTD 351M and put it right back on.

That's odd, I thought the only F250 models to have an after cat o2's were the 05' and up with the new y pipe. My 03' has the o2's on the down pipes from the manifolds and nothing else.

It depends on the weight rating. If the vehicle weighs less than a certain amount the exhaust gets set up differently, and that includes an aft cat O2 sensor. If the vehicle weighs less than that amount it has to pass the same smog certifications as other light vehicles. But if it goes over the weight limit, it qualified for an exemption till '05.


The stock cat is kinda restrictive because they are really too large. Removing them will give you a power boost and better gas mileage, but not as much as if you run the proper cat. We sell a lot of cats on Superduties that have had the cats taken off, and our smaller cat produces a noticeable increase in torque versus a system with no cat. And it flows and sounds a lot better than stock.