OK, first to give a little background on my truck...it is an '01 with a 5.9 and 4WD, and has about 171,500 miles. Last fall I replaced my plenum plate with the Hughes kit and very recently replaced the plenum and intake manifold gaskets again (after my initial install, the plenum bolts backed out after some time and the gasket failed). Who knows how long the gasket was blown before I replaced it the first time, so it's possible the cat got pretty gunked up during that time (though it is not original to the truck).

In the past few days, I've noticed that the truck seems to be getting sluggish, and it kind of sounds like more air is rushing through the air box than normal. Tonight when I got home from work, I put it in neutral and revved the engine a little bit, and the engine seemed to stumble or bog down between 2000 and 2500 RPMs, and it would kind of surge back and forth in that range if I kept my foot on the accelerator. I know there should be a rev limiter, but I know for a fact I have gotten the engine to hit higher RPMs in neutral before, so something seems off.

I just replaced the plenum gasket two weeks ago, and I no longer have vacuum in the crankcase like I did before, so I'm fairly certain that is not the problem. I suppose I could have a vacuum leak, perhaps at the intake manifold gasket. But, I took my time and was very careful to set the intake straight down when I reinstalled it, so I don't think it is leaking. I may do a vacuum test tomorrow to see.

Would a clogged cat cause similar symptoms? Or could it be the pre-cat O2 sensor? I believe it may be original to the truck. I can't justify sinking a ton of money into this truck, as I also have an '08 Hemi Ram with fairly low miles. I use this '01 as my work truck though and would like to keep it on the road as long as I can to keep miles off my '08.

Thanks for any advice any of you can offer!

 

At 171K+ the truck should soon be ready for its 3rd cat under good conditions.
If you had a blown plenum, your cat is toast.
Replace cat and both O2's.

 

So is a cat's typical life span about 60,000 miles under normal conditions? I've always wondered. My current cat has about 54,000 miles, but I suspect much of that was with a bad plenum gasket.

Thanks for your help.

 

Please make sure to come back and tell us what the end result is. What you did and if it fixed it! It helps future people!

 

Maybe closer to 75K under normal conditions... but a bad plenum dumping oil into the system will clog the cat and kill the sensors pretty quick.

 

I've gotten help here with a couple other issues, and I try to post what my results are so other people can be aided as well. Plus, if I do a repair myself, I generally try to make a video of the process and upload it to YouTube. If I end up replacing my catalytic converter myself, I'll try to make a video and will post a link here.

This is a great site!

 

I was thinking about purchasing a universal fit cat and paying a muffler shop to cut out the old one and weld in the new. Is this a bad idea? Is a direct-fit cat a better plan?

Again, this is an older work truck, so I'm hoping to do this repair as inexpensively as possible, but at the same time, I want to do it right. I don't need super performance, just something that will work, and that will keep my truck legal (I don't have emissions inspections where I live, but I don't need a fine for getting caught with no cat).

Any brands to avoid? Any brands I should look at specifically?

Thanks again for your help!

 

I think Magnaflow is your best bet... either a direct fit, or if your doing a custom exhaust, get a Magnaflow universal cat.

 

Awesome to both! Thank you very much! Helps us all, even if we dont necessarily *need* the advice yet!

 

check with your muffler shop before you buy, we have one here that installs a magnaflow for less than you can buy it at the parts store