Catalytic Converter is shot; I think? Help me diagnose!

So I believe my catalytic converter is shot. The truck has been giving me the wonderful P0420. I thought about deleting the converter, but here in Houston we have to have all the lights off and I don't think that's exactly legal. Before I blow some money on a catalytic; I would like some more opinions and make sure I'm reading my charts correctly.

A little history on the truck; it was my little brother's before it was mine and the care was, we'll just say rough. Its been filled with diesel, the engine bay has been flooded once (he left it parked in back and it rained... a lot), and the maintenance record is lacking (he thinks he changed the oil....) Oh, and he got T-boned (he decided to run a stop sign.) Fortunately he's only had it for roughly 8k miles so theres only been so much time for him to do damage.

The truck has 227k miles and is a 2000 prerunner with the 3.4 engine. Good news is the price was right.... $1500, the transmission performs as it should, and the tires are in A+ shape!

When I got the truck it was pulling a P0171 along with several misfire codes. Among a general cleaning I replaced the upstream O2, replaced ignition packs, wires, spark plugs, cleaned fuel injectors, replaced seals on injectors, cleaned TB, replaced MAF, and both plenum gaskets.

I drove it around and tested it out, ended up with a P0420. I pulled the catalytic converter to make sure I still had the honeycomb material, which i did, and replaced the donut seals between the converter and tail pipe (preventative leak measure.) I also cleaned & tested (with multimeter & propane torch) the downstream O2 sensor.

I took it for a drive yesterday & today to and fro school. Everything is running as it should for the 110 miles. But I still have a P0420. I just got my bluetooth OBDII and took some readings from my phone for the O2 sensor readings. They are attached below. B1S1 is from the upstream O2 sensor and B1S2 is the downstream. It seems to me that the catalytic started working for a short period (during the dropped region on downstream O2 sensor) but then failed again. Both of these were taken on the flat Texas highway with cruise control set to 60. The occasional overpass, but nothing special for the road.

So what do you guys think? It looks to me that the catalytic converter is shot? Or is there something else I should check.

 

Replace the downstream sensor before replacing the cat. When they go bad, they go bad and may or may not show any difference in the voltage. Just my .02......

 

I thought about that, so I bench tested the O2 sensor with a propane torch and multineter, I got rapid voltage variations. Also, the 2nd graph is the downstream sensor.

 

they are cheap for the 49 state version, replace them with OEM fit Magnaflow so you dont have to cut and weld.

 

Eastern sells a 49 state for a 1/4 ($40) of the price of the Magnaflow with a 50k warranty. It's backed by Amazon (i've already had to return stuff through them, its pretty effortless; hell they even told me to throw the broken tool away) so I'm comfortable with the warranty. I was planning on cutting the flanges off of the original and welding the Eastern to the flanges.

I realize that I could probably save time by getting a bolt on but as a college student... my time is pretty worthless. Lol. I also have access to all of the equipment, so that should help.

 

Make sure you order the correct engine family code version.

 

I was wondering the same thing on these. if it matters. I have a shop that's gonna do a new system and he said he had magnaflows readily available that he uses. Didn't even think to ask him because at the time I didn't realize even though they say universal, they are designed for specific vehicles. I stumbled upon this after I decided to order all my parts myself, the muffler, resonator, and the cat, so it'd be a little easier on him and cheaper for me by supplying the parts myself. Then have him weld it all up with new piping. Anyways, I discovered that an $80 cat was supposedly the wrong one as magnaflow listed a different universal type for my truck on their site. Which I input the part number on Amazon and it turned out to be a different universal $112 cat that looked to be a bit bigger. So I opted to order that one. Not sure I should be glad I discovered this or not. Who knows if what he would've supplied would've been the correct one or not...

But what's the difference? More flow? They're all pretty much high flow and a straight through design...?

 

What converter did you guys go with? I see several magna-flows online.

I am beginning to be swayed, the price is $35 more, it can be delivered quickly (other one had a 2-3wk delivery...) and seems to have a better warranty.

I'm looking at

$115 MagnaFlow Standard Grade Federal/EPA Compliant Universal Catalytic Converter 94005

http://www.amazon.com/Magnaflow-94005-Universal-Catalytic-Converter/dp/B000COVG8E/ref=cm_rdp_product

Is this what you guys installed? It says it should fit but I always appreciate secondary opinions, these emissions can be tricky tricky.

 

For a little more you can use a high flow. I have used these in the past with great results.

http://mandrelbendingsolutions.com/high-flow-300-cell-cpsi-sports-converter/

 

I am iffy of the high-flow. I've heard of issues arising with the O2 sensor and high flow. Ends up requiring the computer to be reprogrammed to new voltage ranges which requires a trip to the dealer... etc.

Since my taco will hardly be a performance vehicle; I'm happy with the horsepower it makes. I don't see the benefit of switching. I just need it to run and pass inspection, lol

 

Just unplug the battery and let it reset so it will learn the new fuel/air. No dealer necessary.

I had used them on a few BMW's with no issues. Just an option.

 

I learned my lesson with high flow cats with my old 91 civic hatch back, they were made smaller with like 30% less internal wafflecone stuff and didnt improve anything, actually sounded worse cause it really raspy compared to a stock size cat.

I use oem size and equivalent stuff for a reason now, I have 2 new cats that are magnaflow direct fit 50 state versions on the truck installed about 1 year ago.

They never threw a code and only took a few hundred miles to feel like the old ones.

Passed smog that next week after instal with flying colors.

I also have Doug Thorley headers, AEM brute force intake and a whoppin 24 inch body magnaflow muffler with re routed piping to the rear bumper area.

 

I cleaned my T-100 and my neighbor's Tacoma's converters...
http://www.toyotanation.com/forum/60-t-100-forum/423972-code-p0420-catalyst-below-threshold.html

I could build a new Cat Washer and clean your converter.

 

Video explains pretty well how to diagnose a bad cat. I had a 0420 code about a month ago and used a temp gun to diagnose my cat. Replaced it with a direct fit and haven't had the CEL since

https://www.youtube.com/watch?v=9VZ5K8n5jj0

OP hope you got everything squared away.