A friend of mine has a 98 f150 4x4 and said he has 4 catalytic converters on it. Does he need to have all 4 on there for inspection reasons or can he go down to just two. Any reason to have four in the first place

 

There are a million vehicles on the road with modified or aftermarket exhaust systems. It doesn't matter what is under there as long as it will pass emissions (except California, I've heard they check part numbers). If it came with 4, I bet there was a reason Ford put them on there.

I live in a nonemissions county in Texas tho and mine will pass with anything short of me dragging it along the ground behind me.

 

Depends on your location.
Some states do a visual inspection and see if all 4 are there. Some do visual inspection and just look to see if there are cats on. These visual inspectons only look at the outside, so you can hollow the cats out if you wanted (and many do hollow out the 2nd cat on these trucks).
Some areas also have emissions testing along with the visual, so hollowing out the cats won't work (some places you can get away with hollowing out the 2nd cat).

So without knowing your location (which every member should put in their profile if they want their questions answered correctly for them, at least what state) your question can not be correctly answered.

 

I live in Texas

 

Cats are expensive. If Ford could've saved a significant amount of money by having only 2 cats instead of 4, they would've done it. But, they didn't. There's a reason the truck has 4 cats. Removing or gutting cats is a federal crime and is illegal in all 50 states, even if your area doesn't have emissions tests. If they're working properly, why do you want to mess with it? Just leave them on there.

 

There's a few reasons why people do it, the majority being for performance reasons. Also, as you said, cats are really expensive. If they go bad, and you don't have to pass emissions, most people will just take them off since they're restrictive and basically dead weight.

 

I'm a Texas state inspector. The answer to your question about having to have 4 catalytic converters is no, but if your friend's vehicle is registered in an emissions county then the vehicle would have to pass the emissions test. The cats can be changed as long it will still pass and it must also still have a working muffler on the vehicle.....even diesels. Going off of your location on your post Wylie, Texas shows to be in Rockwall, Dallas, and Collin Counties which are all emissions counties. Hope this helps.

 

I just bought my 97 a few months ago. It has no cats and a huge muffler. I noticed the other day that the 4 oxygen sensors were installed on the exhaust pipes even though it has no cats. I do not get a check engine light or notice any real gain by them not being there.

 

Good to know. I always wondered if I could replace the 4 cat system with a 2 cat system if I had issues with the cats.
Since I am in Harris County I have visual and emissions testing.

 

thanks for all the input guys, ill let him know. On that note, what about my 04 f250 6.0 diesel? Do I need my cat and muffler or can I run straight pipes back?