2011 Ford Mustang - Smelly cats

Sulfur smell coming off Cats - this is a recurring issue with the 2011 Mustang V6 and the Dealers just say they can’t recreate the problem - I use the A/C on flat ground at low speeds and usually no problem - as soon as I hit the gas and go uphill or downhill the sulfur comes into the cabin. Lol, Ford is messed up - replace the cats or remove if possible in your State. There was an Extended warranty on them off of a TSB from Ford - but don’t expect them to help you - that’s a joke. I still love my Stang and have found a way to keep the sulfur out of the cabin most of the time - when you are on the highway crack open the passenger side window and leave the A/C off - around town if you drive smoothly the problem will not be prevalent. You know what they say - Fix Or Repair Daily - lol.

NO, do not do this. It is a FEDERAL offense, not a state law. If you do this, you will have a check engine light that will never go off.

I’ve owned 2 Mustang GT’s, and 3 other Ford products and find them to be very reliable. I’ve also never had the sulfur smell, ever.


You are correct Mustangman, and I would not disconnect…but let me tell you - Ford does not back up it’s product like they should regarding this problem - it’s a health issue…

It is an annoyance issue in my opinion.

No , it is a problem with a vehicle that is out of warranty . And this could happen to any brand of vehicle.

Well, I’m allergic to sulfur, but like I said I love my Mustang Dark Red Metallic Black top Convertible Dyno’d at 308 and 288 torque - not a GT but it’s great anyway, my favorite car…got rid of a Challenger for it - our other vehicles are a Porsche Cayenne and an old Benz older E 4 Matic - family cars. But I would love to buy a 2020 Mustang GT but can’t cover it now - lol.

My Mustang has only 20,900 miles on it…

Sulfur or Sulfa-classed antibiotics? not the same thing! :wink:

Depending on when in 2011 your Mustang was made, you still have federal warranty on your emissions system (8 yr/80,000 miles), maybe try an independent mechanic or muffler shop to see if they can figure it out

1 Like

Sulfur dioxide is what comes out of my Cat Converter into the cabin - whatever it’s a PITA and Ford is a joke when addressing the issue

Thanks for the advice I’ll try my Indy

Rather than seeking better smelling exhaust you should find the reason why exhaust is entering the cabin. There are cabin vents behind the rear bumper cover, if one of the vents is damaged exhaust can enter the cabin. Has this vehicle been in a collision?

The emissions system warranty on a vehicle is 8-years, 80K.

Thanks - I’ll try another

Ford Dealer

And leave your ( Fix or Repair Daily ) attitude at home.


Hmm… your car is low mileage, but it is 8 years old. You could run your VIN to determine if it was sold after August 2011, but Ford (or any car company) is not liable for smells. (They’ll probably be happy to look @ their normal hourly rate.) If the car can pass emissions standards, it is not a warranty issue. For issues outside certain emission devices failing (Federal law) the warranty expired years ago.

On the good side, have you searched for the cause(s)? The first popup on Google is: “Other causes of rotten eggs smells can include hot engines or broken fuel pressure regulators. All you might need to do for the latter is replace your fuel filter. A rotten eggs smell is probably the result of hydrogen sulfide. Sulfur is present in gasoline, and it’s converted to sulfur dioxide, which is odorless.”

Of course, if the car was modified, the list of reasons might be longer.

I recall that back in the late 70s and 80s, I noticed a sulfur smell when driving behind Fords, but rarely when behind other makes. I wonder what that was all about.

Thanks - hydrogen sulfide, right as sulfur dioxide is odorless - Got it. I will replace the fuel filter.

Sorry, I couldn’t resist.


I would like to know how that will keep the exhaust from entering the vehicles cabin.


In always liked that woman - funny and beautiful