black sutt in exhaust

[slapnpop]

I've been noticing a lot of extra black sutt coming from my exhaust lately, and am concerned this could me be my cats?
If it is, what are your thoughts on the off road y pipe, as we don't have inspection here! )

Any other things to check as I'll be doing the 60k service next week and will have 1/2 the engine apart?

 

[sdpatt]

That would be black soot and when you burn hydrocarbon fuel, the carbon has to go somewhere. The hydrogen from the fuel and oxygen from the air get together and make water vapor, but the carbon is released as carbon. Your cats can neither create nor prevent the blackness in the pipes. It can be accentuated by a rich air to fuel ratio and cooler ambient temperature that lets the combustion byproducts adhere to the exhaust pipes rather than exit as vapor. Have you replaced your O2 sensors in the last 60,000 miles?

 

[slapnpop]

So the super cold temperatures lately could be a main contributing factor in that trail of black powder going UP the back of my bumper?

I haven't changed the o2 sensor, I'll test them while the car is out next week.

 

[sdpatt]

If you've been getting black trails on your bumper, you could also be buring oil, but I didn't want to get into that.

Scott