How to determine bad cat on FI

schmeky

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Developed a slight rattle under the car recently. Put it on a lift and we inspected everything under carriage from the front of the engine to the tail pipes and found nothing loose or touching.

We tapped the LH side cat and it was solid. Tapped the RH side cat and it sounded different, like something was not quite right compared to the LH side.

Might be my imagination but it feels down on power as well. No codes. Drives smooth as ususal.

How can I tell if a cat is going out? Any way to test?

 

engineermike

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1. Remove cat and inspect from inlet and outlet.
Or
2. Put borescope in o2 sensor hole and inspect upstream element.
Or
3. Measure exhaust pressure at full load.
Or
4. Log rear o2 sensor voltage and plot over time. A bad cat will show frequent high/low switching.
 

Jackson1320

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If you blow the cat out you will get a code. If you melt it then you are going to feel like it is down on power. It will get worse and worse and you will feel it more with rpm
 
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schmeky

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Thinking about getting a take off 2018 - 2020 exhaust manifold set, removing the cat interior and welding in a SS tube of the appropriate diameter to make a straight through (not originally my idea) shot for the exhaust gases.
 

Jackson1320

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Keep the cats and just clear everything out of them. That way if anyone looks it will look stock
 


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schmeky

schmeky

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Jackson1320,

That's exactly my plan. Keep the "canister", less guts, and simply weld in the appropriate tube.
 

mangosmoothie

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Idk if there’s data on mustangs but on mazdaspeeds gutting the cat caused a lot of turbulence. The best fix was to weld a straight pipe through the cat area if you wanted to keep it looking stock.
 
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schmeky

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mangosmoothie,

That's exactly what I said.
 

 
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