Fouled a o2 and blued one of my new cats

[motorholmes]

The thing is dark colored and looks like crap. I put a bit of sensor safe copper silicone on the surface of the header that the cat clamps to. It must have fouled out the rear o2 and made the passenger bank run way lean. I only ran the truck for a little while to look for leaks and listen to my mufflers, and it was enough to blue the hell out of my new cat.

[George C]

rear 02s have nothing to do with AFR control. they are there to tell the PCm that the cats are good or they arent. They have zero effect

[motorholmes]

What do you think made the cat get so hot? I just assumed it was a lean condition

[Madd Maxx]

Cats get too hot from a rich condition, not lean. Excess fuel entering the cat ignites and burns when it hits the hot core. If it gets too hot, the core will melt and cause flow issues. Your fouled O2 sensor is probably the culprit.

[George C]

What do you think made the cat get so hot? I just assumed it was a lean condition

you should be able to answer that yourself. if you have HPtuners you can tell exactly what went wrong with the truck

[motorholmes]

Cats get too hot from a rich condition, not lean. Excess fuel entering the cat ignites and burns when it hits the hot core.

Just for the record, I have to strongly disagree with this statement. Ask any Harley owner what happens when you put better flowing pipes and k&n on a stock bike. Pipes blue up real bad from lean fuel. Unburned fuel getting into the exhaust would have to be caused by a whacked out timing issue. If the timing is correct you can run it as rich as you want and it will still burn it all.

[George C]

Just for the record, I have to strongly disagree with this statement. Ask any Harley owner what happens when you put better flowing pipes and k&n on a stock bike. Pipes blue up real bad from lean fuel. Unburned fuel getting into the exhaust would have to be caused by a whacked out timing issue. If the timing is correct you can run it as rich as you want and it will still burn it all.

there is a point where to much timing doesnt do anything and can hurt you. to rich will destory a motor just as to lean

also the reason the harley or any other vehicle runs lean from free flowing exhaust and air filter is the fueling is setup for a more restrictive setup. so freeing up the air flow wil lcause you to be leaner and youll have popping issues on decel or letting off throttle.

if you would tune for it or rejet the carb for proper AFR you wont have issues

[Madd Maxx]

Cats get too hot from a rich condition, not lean. Excess fuel entering the cat ignites and burns when it hits the hot core.

Just for the record, I have to strongly disagree with this statement.

From: All Catalytic Converters - Catalytic Converter Failure

Excess Fuel Overheating The Catalytic Converter
An engine that is performing at peak efficiency will burn all the fuel in the combustion chamber during the combustion process. An engine that is not performing properly, that is not burning all the fuel, will allow unburned or excess fuel to enter the exhaust system. When this excess or unburned fuel contacts the hot core of the converter it will ignite. This constant infusion of unburned fuel will cause temperatures to continuously rise above the designed operating temperature until the core of the catalytic converter will actually melt.

From: Catalytic converter - Wikipedia, the free encyclopedia

Any condition that causes abnormally high levels of unburned hydrocarbons — raw or partially-burnt fuel — to reach the converter will tend to significantly elevate its temperature, bringing the risk of a meltdown of the substrate and resultant catalytic deactivation and severe exhaust restriction.

There are many other reputable sites that I could quote, but I think you get the message.

[motorholmes]

OK I got ya. I'm just sayin my condition has nothing to do with bad valves, low compression, or whacked timing so the unburned fuel theory is not working.

Let me re-phrase: I do agree with your statement, but not for this situation.