Possible Cat Converter Problem.

• Often smell rotten eggs when getting out of Tahoe (have tried different fuel), but not every time
• Have now smelled it inside the cabin for a few seconds (twice) while on the highway
• I can see what looks like a black burnt spot on corner of the muffler if that matters
• Haven't noticed any holes anywhere but will look again
• There's a slight but constant metallic rattle that I can't find after removing the entire interior panels (possibly coming from under the vehicle?)
• No CEL or codes

BourbonNcigars said:

Noticed I'm getting the telltale rotten egg smell (no matter where I got fuel) when I get out of my 2010 Tahoe (113K miles). More worrisome is that I've smelled it inside while driving 70mph. I was quick to blame my daughter but I knew what the smell really was. I've never messed with exhaust systems before but I know that smelling anything related to the exhaust inside the cabin is no bueno.

Here's the small amount that I do know:

• Often smell rotten eggs when getting out of Tahoe (have tried different fuel), but not every time
• Have now smelled it inside the cabin for a few seconds (twice) while on the highway
• I can see what looks like a black burnt spot on corner of the muffler if that matters
• Haven't noticed any holes anywhere but will look again
• There's a slight but constant metallic rattle that I can't find after removing the entire interior panels (possibly coming from under the vehicle?)
• No CEL or codes

What's my next step here? Any help is appreciated.

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kbuskill said:

If you have an OBD2 scanner that hooks up to your phone you can download the Torque Pro app and monitor your cat temperatures via the down stream O2 sensors. That would give you some more info.

Alternatively, if you have an infrared thermometer you could slide under the truck while it's running and up to temp and check the temps pre and post cat.

Also you can get an inspection camera that plugs into your phone and then pull the up stream and down stream O2 sensors and insert the camera to get a visual of the catalyst's condition.

OR you can take it to an exhaust shop and have them check and diagnose.

I see roughly 565° after idling for 15-20 minutes when the engine is up to temperature. And upwards of 11-1200° while cruising at highway speeds depending on speed and load. These temps are gathered via Torque Pro from the down stream O2 sensors.

Rotten egg smell and a possible rattle are pretty good indications of a failing cat though.

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BourbonNcigars said:

Thanks. I do have a thermometer to check the temps with. What am I looking for exactly? Similar to what you're getting above I assume...

Say it is bad, though...what's the replacement options? Dealership or aftermarket the way to go? I have zero desire to have a louder exhaust. I'd actually prefer a quieter one if such a thing exists in the aftermarket exhaust world.

Also concerned with why it'd go bad at 113K miles. I've had several vehicles with way more miles that didn't have an issue with a cat. Makes me wonder what the root cause is.

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swathdiver said:

Stephen, what grade and brand of fuel are you running? Do you frequent the same station or go wherever convenient? Low tier fuels or even Shell's 87 are known for high sulfur content and making these smells. They cats are doing their best but too much sulfur and they can fail. Switch fuels, maybe run some E85 through the system and see how it goes.

I can offer some advice if the problem is the cats.

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kbuskill said:

Also you can get an inspection camera that plugs into your phone...

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BourbonNcigars said:

Thanks, James. I've been going back and forth between Shell 87 and Exxon 87, which is the same fuel I've used in every other vehicle for the last 15 years without noticing any odors. I don't think I have any E85 options near me.

Wish I had more clues to give. I do notice a decent amount of black soot around the exhaust tip...no CEL or codes...intermittent rotten egg smell when getting out of the vehicle (and occasionally while driving)...a rattle that may be coming from underneath...that's about it. To be honest I really don't have enough time with it to know what kind of mileage I'm getting, or to know if power output is diminished. I have nothing to compare it to since I've only had it about 6 weeks. I only just started tracking the MPG since this issue came up.

I'll fill up with fuel on my next tank at some other station. Anything else a layman can check?

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