Greetings everyone I have a new post regarding my catalytic converter. In the last 3 wks I started hearing a rattling noise underneath my truck during startup lasting for about a minute then going away. This weekend while changing out the TPS and coil I started the engine and heard that rattling noise. When i crawled under the truck it was coming from the catalytic converter. I pressed on the heat shield before it got too hot and it wasn't the source. Does this mean the Cat is about to fail or need changing? The rattling would stop after a minute or two.

 

If your cat sounds like a can with marbles in it then yes you need to do somthing about it. Do you need to replace not neccesaraly . You could just gut it.

 

Yeah it sounds like marbles rattling around in there. If I gut it will that affect my o2 sensor causing check eng lights and poor performance?

 

It will most likely cause a cel light but, it won't have any downside in performance. The O2 sensor after the cat is only there to tell you if the cat is not working efficently. It doesn't change anything else. So obviously when the cat is gone the after cat O2 sensor has a chance at triggering a cel. It won't always trigger a cel and there are ways to remedy it. You can build or buy an O2 similator or install parts on the O2 bung so it is out of the flow of exhaust but, still in the pipe.

 

Is there an after-cat O2 on your truck? There wasn't one on mine. If theres not, there wouldn't be a CEL...

 

Oh yeah there's one on there. I replaced them about 4 months ago.

 

Ok I'm listening!

 

to what?

 

i believe he actually means "reading" but meh it close enough

and perhaps he is reffering to a specific way on how to fool the O2 sensor?

 

Do a search for O2 sensor. There is a post that I made a while ago that has links to wire diagrams to make a similator and there is a link for a low tech way to fool it.