Removing third cat temporarily due to bad rattle

[Davies0202]

The third cat on my 02 4.6 mountaineer started to rattle badly so I can assume it’s grenaded itself. If I remove it and replace it with straight pipe for a month or two until I have access to a welder and another cat will I harm anything? I don’t intend to keep it like this but it sounds like my engines gonna blow and I’d rather not drive around it with for a month or two rattling away.

 

[TechGuru]

I don't know the 4.6 off hand, as long as there is no O2 sensor after the CAT it should not hurt anything...

 

[Davies0202]

Alright thanks

 

[mountaineer2004]

It won't do anything, except make your exhaust a bit louder.
This includes emission tests. Don't ask me how I know.

 

[TechGuru]

It won't do anything, except make your exhaust a bit louder.
This includes emission tests. Don't ask me how I know.

Well ya, if there is no sensor after the 3rd CAT then there is no way to trigger a code in the computer that will fail the emissions test. Now areas that don't use the OBDII and use a sensor up the tail pipe there could be a problem...

 

[iowa_hick]

You can put a spacer between the O2 sensor and the pipe to trick it into seeing different flow than the upstream sensor so it doesn't trigger a code.

 

[Mbrooks420]

This will turn into a permanent temporary solution.

 

[Davies0202]

Well ya, if there is no sensor after the 3rd CAT then there is no way to trigger a code in the computer that will fail the emissions test. Now areas that don't use the OBDII and

This will turn into a permanent temporary solution.

If I’d pass emissions I would, I wouldn’t mind the extra sound

 

[Davies0202]

The third cat on my 02 4.6 mountaineer started to rattle badly so I can assume it’s grenaded itself. If I remove it and replace it with straight pipe for a month or two until I have access to a welder and another cat will I harm anything? I don’t intend to keep it like this but it sounds like my engines gonna blow and I’d rather not drive around it with for a month or two rattling away.

Just an update for anyone in the future no check engine light after about 200 miles engine runs the same if not a little better can’t tell if the extra mpg is me backing off cause its louder or if it’s running better either way nothing bad happened so far.

 

[FPGT24]

Theres no harm done in removing the 3rd cat as long as you see no o2 sensors after the cats....IIRC, Ford changed o2 sensor locations twice i believe on the 3rd gens. Alot of the guys with the 4.6 remove the 3rd cats to get a better exhaust note when putting on a performance muffler.

 

[Mbrooks420]

I think what you actually mean is it won’t harm performance. It’ll certainly put out more emissions. And, be a federal crime.

 

[Davies0202]

Theres no harm done in removing the 3rd cat as long as you see no o2 sensors after the cats....IIRC, Ford changed o2 sensor locations twice i believe on the 3rd gens. Alot of the guys with the 4.6 remove the 3rd cats to get a better exhaust note when putting on a performance muffler.

Yer no oxygen sensor after the third cat it’s a few inches before it, on a 2002 mountaineer atleast

 

[Davies0202]

I think what you actually mean is it won’t harm performance. It’ll certainly put out more emissions. And, be a federal crime.

Yeah I was gonna replace it but I just dropped $1500 on a transmission rebuild so my exhaust being a tad bit louder doesn’t bother me I already have no muffler haha. I was mostly worried about making my engine run wrong and the exhaust smelling like eggs but honestly it smells the exact same and drives a little better.

 

[Mbrooks420]

You can’t smell a lot of the junk the catalytic converter burns off. It’s surely there.