Catalytic converter replacement?

[mntn-biker]

Anyone on the board here have to replace their catalytic converter and if so, did you go with a dealer OEM or a Magnaflow or some other brand? My mechanic says he hasn't had much luck with the aftermarket brands and that he never sees an OEM cat from a dealer ever come back to his shop. He's a standup guy, known him for years so it's not like he's feeding me a line on getting a more expensive part just to spend my money. He's just worried if I go aftermarket that I start getting a P0420 code again in a year or 2. He says the dealer ones cost more since they contain more of that precious metal that makes these things cost so much.

[jayoldschool]

He's right... BUT... the question is... WHY is your cat bad? They don't go bad by themselves. Putting a new cat on is like putting a band aid on a gunshot. You've got to fix the problem before you replace the cat.

[gtv237]

He's right... BUT... the question is... WHY is your cat bad? They don't go bad by themselves. Putting a new cat on is like putting a band aid on a gunshot. You've got to fix the problem before you replace the cat.

That's a very true statement. Although they can just go bad by themselves. Like if the substrate crumbles apart. Of course when they clog or become inefficient it's usually because of a problem with the engine.

My opinion on converters is, NEVER use a universal converter. They will usually only last a couple years at best. Direct fit converters are tons better. With a properly running engine you should be able to get many years out of a direct fit. Obviously the best quality is going to be OEM. But if you have an older engine (100k+), the best compromise would be direct fit. After 100k the engine's internals and sensors get gunky and become less precise.

[mntn-biker]

Ok, I thought with 147,000 miles on a 2003 base model, a cat might just go bad so what might cause a cat to go bad if it's not crumbling? I just replaced the plugs less than 10,000 miles ago. Also cleaned the throttle body too. My mechanic also mentioned that the O2 sensor after the 1st cat could be going bad but not likely if I am only throwing the P0420 code at 75mph highway speeds for an hour or more and not just riding around town.

[gtv237]

Ok, I thought with 147,000 miles on a 2003 base model, a cat might just go bad so what might cause a cat to go bad if it's not crumbling? I just replaced the plugs less than 10,000 miles ago. Also cleaned the throttle body too. My mechanic also mentioned that the O2 sensor after the 1st cat could be going bad but not likely if I am only throwing the P0420 code at 75mph highway speeds for an hour or more and not just riding around town.

It's usually rich conditions that cause the cat to go bad. It's the carbon that builds up on the platinum that does it. Rich conditions can be from so many different things. The sensors that control the air fuel mixture can be dirty, the fuel injectors can be leaky, spark can be weak or out of time, oil could be leaking into the combustion chamber through the piston rings, valve seals or elsewhere.

[jayoldschool]

Remember, the post-cat O2 only tells the computer that the cat is working. So, here is what I would do first. Put a fresh O2 in the pre-cat location, and move the old one to the post cat spot. Clear codes, drive, and watch your e-ready flags.

[mntn-biker]

....e-ready flags.

??? Do you mean watch and wait to see if I get another P0420 code?

Sounds like the pre and post cat O2 sensors are identical?

[gtv237]

....e-ready flags.

??? Do you mean watch and wait to see if I get another P0420 code?

Sounds like the pre and post cat O2 sensors are identical?

I think he means to wait for the monitors to clear.. And no the sensors are not identical. Electrically they are but the first O2 has much shorter wiring.

I'm not a fan of just throwing new parts on without verifying yhthe condition. There is a way to test everything. If you have enough miles on the spark plugs you can inspect them to see if there is a rich condition or oil leaking into the combustion chamber.

[mntn-biker]

....e-ready flags.

??? Do you mean watch and wait to see if I get another P0420 code?

Sounds like the pre and post cat O2 sensors are identical?

I think he means to wait for the monitors to clear.. And no the sensors are not identical. Electrically they are but the first O2 has much shorter wiring.

I'm not a fan of just throwing new parts on without verifying yhthe condition. There is a way to test everything. If you have enough miles on the spark plugs you can inspect them to see if there is a rich condition or oil leaking into the combustion chamber.

Could my local Advance Auto Parts store test the O2 sensors on the vehicle or would I need to bring it to a mechanic or dealer with the "big computer"?

[jayoldschool]

If you have an Android phone, you can test the O2 functions yourself with a $15 bluetooth adapter, along with the free Torque App.

Yes, I was referring to the monitors. And, sorry, didn't know the wiring was different for the pre and post O2s.

[gtv237]

You can't really test O2 sensors. If one has failed electrically, it will throw a code for it. The only way an o2 could cause a 420 is if it still reads but is reading inaccurately. And even then it would have to be within range, which is rare. Besides if it was reading incorrectly, the air/fuel ratio would suffer and you would be able to tell by the plugs.

[jayoldschool]

You test them by watching the mV output in real time. They will get lazy before a code is thrown. Additionally, the rear O2 does not control AF mix.

[mntn-biker]

If you have an Android phone, you can test the O2 functions yourself with a $15 bluetooth adapter, along with the free Torque App.

Yes, I was referring to the monitors. And, sorry, didn't know the wiring was different for the pre and post O2s.

Found what I think might be a similar app for iPhone but I have no experience with this. What do you think? Comparable?

https://itunes.apple.com/us/app/engine- ... 57194?mt=8

[gtv237]

If you have an Android phone, you can test the O2 functions yourself with a $15 bluetooth adapter, along with the free Torque App.

Yes, I was referring to the monitors. And, sorry, didn't know the wiring was different for the pre and post O2s.

Found what I think might be a similar app for iPhone but I have no experience with this. What do you think? Comparable?

https://itunes.apple.com/us/app/engine- ... 57194?mt=8

You'll need software that can data log and provide graphs. A simple real time reading will do you no good unless the o2 is really bad or dead. In which case the computer would have surely noticed and thrown a code for it.

[mntn-biker]

I'm guessing the scan tool I use to read and clear codes (HarborFreight) probably won't work either?

http://www.harborfreight.com/can-obd-ii ... -9479.html

[jayoldschool]

If you have an Android phone, you can test the O2 functions yourself with a $15 bluetooth adapter, along with the free Torque App.

Yes, I was referring to the monitors. And, sorry, didn't know the wiring was different for the pre and post O2s.

Found what I think might be a similar app for iPhone but I have no experience with this. What do you think? Comparable?

https://itunes.apple.com/us/app/engine- ... 57194?mt=8

You'll need software that can data log and provide graphs. A simple real time reading will do you no good unless the o2 is really bad or dead. In which case the computer would have surely noticed and thrown a code for it.

Torque does that

No, a simple code reader won't do it.

I don't have experience with the iPhone apps, but others have reported that they aren't as good.

[mntn-biker]

Hmmm.... Don't have an Android phone Guess I'll start with pulling and checking my plugs. Then I guess I'll have to talk to my mechanic. I believe he said he could check the O2 sensors.

[jayoldschool]

Yes, he'll have a scanner that will do the same thing.

[mntn-biker]

I found this $10 app OBD Fusion:

https://www.obdsoftware.net/software/obdfusion

and e-mailed them asking about reading and logging O2 sensor data and here was their response: "Yes, OBD Fusion can read O2 sensor data (as long as your vehicle supports it). It can log data to CSV file, and it can also graph data."

Now the next question is, are all of the ELM 327 wifi scanner plugs pretty much the same? They state, "OBD Fusion works with all ELM327 Wi-Fi adapters". They have 1 for sale but it's $120

Thinking about going this route to check my O2 sensors if I can get the app and plug for $25 or less so I'm not out a ton of dough.

I did put the car up on jacks and banged on the cat with my hand but didn't hear any suspicious rattling just as my mechanic suggested I may not.

[KingGeorgeXIII]

Hey guys, I'm an engineer and I calibrate OBDII monitors for a living, though I don't work for Toyota. For the record, 150,000 miles is considered "Full Useful Life" of a catalyst, so it's not unreasonable for the cat to just be tapped out. That said, since we have to be emissions-compliant at FUL, there should generally be considerable life left in a cat at that point. To make "bad" cats for demonstrating that our monitors can fail P0420/P0430 before the emissions degrade past the legal limit, we destroy a catalyst (through a repeatable laboratory process) considerably worse than we do a "150k" cat.

In a nutshell, catalyst monitors work by comparing the signal from the upstream and downstream O2 sensors. A good cat acts as a capacitance in the system and "smooths out" the voltage. A bad cat doesn't. If the signals are too similar, the cat is failed. Because a of this, a "lazy" upstream sensor can cause premature failure. There is a diagnostic for each O2 sensor, however it does not have to fail unless the sensor has degraded enough to cause the car to fail an emissions test, which may or may not be more than enough degradation to cause false failure of Cat Mon, depending on the application. Calibration measures can be taken to compensate for all of these things, but I don't know if options that sophisticated were available back in '03, which is well before my time.

Now that the lecture is out of the way, my suggestions:

1. Give it an "Italian tune-up". This is the least work on your part. Sustained WOT acceleration will get the cat extra hot to burn off the deposits that can reduce it's efficiency. Puttering around like a grandma can and will coat a cat with dust. A few repeated 30-75 mph runs should do the trick. Coast down between each run with your foot OFF the gas so that the fuel system is shut down, blowing cool, fresh air though the cat to burn off residual fuel and thermal cycle it.

2. Swap your upstream and downstream O2 sensors (may be difficult or impossible without splicing wires, based on what others are saying re different length harnesses). The downstream sensor is exposed to less punishment, and may be better. Also, having a "lazy" downstream sensor has the opposite effect as a lazy upstream one, making Cat Mon pass a bad catalyst. We have to diagnose a sensor that's bad enough to interfere with detection, but if you're only marginal, this may do the trick.

3. Replace your upstream O2 sensor. A gamble. Cheaper than a cat, won't help if the cat really is bad.

4. Check for exhaust leaks. These can do weird stuff to the system. You'll need special tools and/or professional help to do this right, which I wouldn't bother with unless you can obviously hear a leak.

Good luck!