Cat starting to come apart

[Dirtautoguy]

Today I noticed my o2 sensor wire was hanging down under my truck ( it had fell down fairly often since i got the truck) and while I was under there I decided to beat on my catalytic converters and see if there were any loose chunks in in them. And in one there is just what sounds like little pieces rattling around and the other one sounds solid as far as pieces rattling. I don't think the o2 sensors have ever been replaced nor the cats. But I also don't have any codes for It and the truck seems to run fine.

 

There is no emissions testing or anything here.

[Chris]

Then cut the cats off, have the rear O2 sensor tuned out

[Dirtautoguy]

How will that effect mileage and how it runs?

[Chris]

It will run better than a busted cat. At minimum throw on some high flow cats

[Dirtautoguy]

If it was bad though wouldn't I be getting an inneficiency code?

[Chris]

You should be, but my right cat went and I didnt get a code

[aflesch]

You can check them with a laser temp gun. The temp at the back side of the cat should be about 100° hotter than the front @ 2000rpm once they are up to temp.

[Dirtautoguy]

Yeah I think I'll try that and see cant you also see with a vacuum gauge? And would my scan gauge work to see too because it shows me manifold absolute pressure or is that different then the vacuum gauge?

[Carder09]

Do you have any state smog inspections in your county that your truck is registered in?

[Dirtautoguy]

Nope I'm just wondering if it is hurting my performance/mpg

[aflesch]

If you have a scanner that reads live data you can look at the O2 sensor readings for the downstream sensors (B1S2 and B2S2). They should be holding steady somewhere between .5 & .8V at 2000 rpm. If one of them is bouncing all over the place or reading really low (<.4V) then that cat is bad.

[aflesch]

The MAP sensor will give you a reading of vacuum but that will only give you an idea if you have a clogged cat. Not one that is coming apart or just not functioning any more. It is not a foolproof diagnosis even for a clogged cat. The temp readings and O2 sensor reading are almost foolproof for diagnosing a clogged or non-functional cat. If you suspect a bad O2 sensor then use the temp method. If you have a known good O2 sensor then just use its readings.

[Carder09]

Sawz all them things off then run to a muffler shop to weld some pipes in its place then call it done.

[Dirtautoguy]

So I haven't looked into it much however I found out that amazon is having a sale and I can get ac delco brand new o2 sensors for about $20 each! And far as I know they have never been replaced would it be smart to do the o2 sensors?

[Dirtautoguy]

And the cat?