Hey guys, just thought I would see what kind of responses and info I can get on this subject since I'm lacking knowledge about it aside from what I have gathered from the search feature (which is quite a bit!).

I have over 150k miles on my truck with the stock cat and o2 sensors. It still appears to be running just fine, but I know how these cats don't typically last this long. I also know I have to replace my plenum gasket again (and yes, I will be going with the Hughes kit without a doubt).

My question is, when I do the Hughes plenum kit, should I also replace the cat and o2 sensors? I have heard that a bad plenum can cause the cat and/or o2 sensors to fail. Is this true? I just don't want to spend the cash on a new high flow cat and sensors if it is unnecessary. Any input is greatly appreciated. Thanks fellas.

 

I say dont replace it unless you forsee a problem with it. Unless your looking for performance gains. Im going on 240k miles with the stock cat and its still working great.

 

get a highflow it will make your truck louder and give you a lil power

 

I'm amazed that you are on the second plenum gasket, but still the original cat. Maybe the plenum was caught in time. Or maybe the previous owner has already gutted the cat. And as far as the 02's go(and the cat for that matter), if it ain't broke , don't fix it.

 

Congrats... you only have to change it if it is going bad, have a cat temp test done and it will tell you how good the cat is.

 

I would not count on your O2 sensors being accurate. It is recommended they be changed every 65K miles. Just because they don't throw a code does not mean they don't go bad.

The cat should outlast the truck and never need changing.

 

Well, I'm not really on my second plenum, puuuursay. A few years back while I was doing a tune up 2 spark plugs broke off in the head. I got one out with an easy out, but the other one I couldn't so I had to take the head off. While I was in there I figured I would replace the plenum gasket since I knew it was troublesome, but was too stupid/uneducated to know about the Hughes fix, and I used the stock replacement gasket/setup. Well, now its already leaking.

As far as previous owner goes, there isn't one. I bought it brand new in fall of 99. So I know the entire history of the truck. The cat is definitely stock and not gutted. On a side note, I did cut the stock exhaust off after the cat at around a few hundred miles (hey, I was an 18 year old punk).

So, basically I have only been driving it with a small plenum leak for about the last few months. Maybe the cat and 02 sensors are fine and I'm just being over cautious?

Thanks for all your help and responses guys.

 

Really? Thats weird. I have seen several Dodge converters completely clog up and hardly let the motor run or the truck drive... some even before 100k miles.

Well, I guess you did say it SHOULD outlast the truck, but in reality I think most don't.

 

yep, they "should" last that long, but so "should" the intake gasket. Mine cat's still good at 108k and I hope it never goes bad. I haven't heard great things about aftermarket quality. Btw, I got a letter a few years back about a recall on the cat but I was already past the mileage or something. As for the 02, get a new one in front of the cat as that's the one that feeds the pcm the info it needs for proper operation. The rear one is just to make sure the cat is still working. I replaced the front one at about 90k as a maintenance item.

 

My cat was still clean when it was...inspected at about 160k, completely clean actually....maybe has something to do with keeping it at a high temp often? I was a punk too once too...

But with the o2 sensors, they do get slow with time. Some vehicles have a "slow response" code or something similar to monitor their condition, i've never seen it on these trucks, it may or may not monitor that. If you have access to a scan tool, you can check to make sure it's getting to below .2 and above .8 volts, and switching several times a second...can't remember offhand how many times is considered good. but changing it after that much mileage is a good idea anyways. Especially with oil contamination from your leaky plenum.