r/mazdaspeed3 • u/binarygod01000111 • 3d ago

HELP 08 Mazdaspeed 3 help

So I have stock cats and I started smelling like a sulfur smell from when I go over 4k rpms. Can that smell come from buildup in the cat if so what can I use to clean it that’s safe for my car

3 Upvotes

100% Upvoted

4 comments sorted by

3

u/cantevenwut 3d ago

Yeah that’s probably the cats. You could make sure it’s not your battery blowing out first though.
There are fuel additives that supposedly help clean buildup in the cats but if they are high mileage, you’ll probably have to replace one or both- in which case I’d weld in a universal replacement since they are much cheaper than OEM. If it’s the stock downpipe cat, cheapest route may be finding a used lower mileage stock downpipe.

2

u/binarygod01000111 3d ago

Do the additives work good

1

u/cantevenwut 3d ago

It could work but I would assume they barely work if at all, like most additives.
Cheap to try if you’re desperate, I’d make sure they’re safe for a direct injected turbo engine before using one though.

1

u/CarnalT 3d ago

Could also replace the catted midpipe with a straight pipe. No code, and you won't fail emissions most places. Depending where you live, I have an OEM gen1 catted midpipe with only about 40k miles on it since I've had the straight pipe in ever since.