Rudy97

Hey everyone.

I'm in need of some serious help. I've gone through 3 catalytic converters in the last 6 months, the last two in the last month and a half. What could be causing them to go so quickly? I bought the truck in late June and about 500 miles in I was told the catalytic converter had failed (I don't know whether it was oem or not). Well after that, I put $1200 into a custom mandrel bent exhaust. What does $1200 get as far as exhaust goes? Well I got a performance header, bent and welded piping, and a magnaflow cat and flowmaster 40 muffler. This set up worked until I went off roading with a bunch of YT members when it threw a P0420 code. A P0420 code says that the catalytic converters performance is below average or that the cat failed/died.

So...I brought it in to the shop. On the first visit they said there was an exhaust leak and that they added 2 more gaskets before the cat and 1 after to hopefully seal it better. That visit cost me $200.

A week later the light was on. I brought it back to them and let them drive it around for awhile. It seemed like the light didn't come back on immediately after I cleared it, sometimes 20 miles later, sometimes 120 miles later. They told me this story about how they had received a batch of "bad" catalytic converters and that that was the root cause of all the problems. They replaced it with another one and didn't charge me(which when I got home I looked under the truck and it's a no-name brand. No markings at all...so I basically paid for a magnaflow and got a no name).

Yesterday, my girlfriend and I were driving home from a party and the CEL randomly comes on AGAIN! I scanned it and it read a P0420

Now I'm going to take it to a toyota dealer for diagnostics and show the shop I've been going to the print out and get it fixed and (in a perfect world) a refund.

Is it shotty workmanship or is there something else wrong with my truck?? I want to be done with this nightmare!

paynemw

First.... don't bring it to the stealership, check it out bro... Underdog Racing Development has this thing called a sensor simulator which will rectify the problem. This is whats going on. Your old cat was more restrictive and lets say um did a better job of not letting the bad stuff get out of your tail pipe.... well your magnaflow cat is a badass and is much speedier and less restrictive... so your O2 sensor below threshold (aka the O2 sensor past the cat) is throwing a code because the readings its getting from the exhaust is out of the range that it "thinks" is acceptable and sends a message to your ecu saying theres something "screwed up" with the engine and to change the air/fuel mixture or some hoopla like that to fix it. Well like i said this thing from URD is a sensor simulator, what it does is make the O2 sensor not flip out when it gets these readings about the exhaust being funky because the badass new cat is less restrictive and "tricks" the ECU so that the computer will continue to run like it should if you still had your original cat in there.... You pickin up what I'm putting down? I had the same problem so its all good. Oh yea the simulator takes about 10 minutes to put in. Good luck bro

Rudy97

But with that sensor simulator one could even eliminate the Cat all together couldn't they? One of my friends chopped out his cat on his WRX and replaced it with a resonator. He then just put a resistor where the post cat O2 sensor is and the car thinks everything is running fine. I'll look into this simulator, but the thing that worries me is the fact that my shop replaced the magnaflow with an offbrand non-performance cat. Either way. I'm taking it back to them and having them replace the cat again.

paynemw

get that old magnaflow back... well the thing is im not exactly sure how the it simulates... but i tell you what call up URD and ask them, they are very informative

74k30

You might have excess fuel dumping into your cat. On my Audi the check engine light turns on when you have problems, but it flashes when you have a problem that might affect your cat, and thats the only time it flashes. I.E. big problems. Dumping fuel down the exhaust. Cats are expensive, as you know. Check your systems dude. You might be flooding your cat with gas.
If all else fail then get a brand new one and don't put it on til its time to get sniffed. run a hollow one in the mean time and don't worry about it. Just enjoy the extra power and the good sound.

BigBallsMcFalls

I'll bet it was just the rear o2 sensor...and nothing related to the cat at all

URD will avoid a code but won't solve a problem except let you pass inspection illegally
in states which care about emissions

paynemw

you have to do a sensor simulator with an aftermarket cat to avoid not throwing a code... the only solution to being completely legal in all states is going back to the original cat which is MAD expensive. and yea it isn't the O2 sensor, because i replaced BOTH my above threshold and below threshold sensors when i put on the magnaflow high flow cat and it STILL threw the code... and it is definately related to the cat... i did plenty of research after having the same problem you are having

YotaNewbie

Unfortunately you can't use a non-OEM cat in 4runners from certain years, I think it's any that are OBDII with the CA dual cat setups. I have a '99 SR5 and I just had to replace a cat this past spring.

I had been kicking that same P0420 code (terrible abuse of "420" if you ask me, Toyota) for like two years and replaced my MAF and both O2 sensors before relenting and replacing a cat. The light went out - but it's come back on twice now for extended periods and then gone off again.

It cost me about $2,100 altogether to replace all those parts chasing a stupid CEL, but in Mass you can't register your car unless it passes inspection, and regardless of what's coming out of the tailpipe if you've got that light on in your dash the computer is failing you every time. It's an expensive and frustrating situation to be in.

If your state doesn't require OBDII-type testing for emissions, then I'd say look into the bypass you can read about on this site. Otherwise, you'll probably have to go OEM with the car or risk perpetual CELs.

hross14

YEP--YOTANEWBIE hit it on the head. CA emissions use the small two CAT system and if you use anything else it will throw a code. The OEM cats had alot more catalyst material in them (thats why they get stolen) and do a better job cleaning the exhaust. The folk lore about making the exhaust flow better when you remove the cat is just that--folk lore.

You can get the scan tool to see what the pre-cat air/fuel ratio is and whether or not everything checks out. which is probably fine considering you are not throwing any pre-cat codes.

If everything checks out--get the URD item and write your congressmen and tell them this whole ubber NAZI like emissions stuff is getting out of hand--especially when they give the manufacture a monopoly on the replacement parts (cats).

roland750

Not all Ca. vehicles have 2 cats. My 96 5 speed only has one and is factory OEM. That said you'll have to use a factory CAT because it has more platinum in it and does a much better job. From what I've heard you'll get a CEL if the CAT falls below 85% effeciency.

nah2323

hross - what scan tool do you speak of?

Dennis140

not to change subject or anything just wondering i have no cat and my check engine light isn't on shouldn't the low threshold throw the code?

Potomacduck

YOTANEWBIE did hit the nail on the head.

I hear about guys chasing an extra 10-15 horsepower or trying to save some money by using aftermarket parts, only to discover that these 4Runners are designed to operate one way - the way Toyota designed them. I could write a book about why this occured, but suffice it to say......aftermaket parts screw things up.........regardless of the anecdotal examples on the internet.

I know this isn't what you want to hear..............Get rid of the exhaust, go back and buy the factory cat(s) and probably install a new MAF while you are at it. If that's too expensive, sell the truck and start in with another truck.

.................................................. ................................

Rudy97

Unfortunately, if that's the case. I'm just going to sell the truck and go without a vehicle till I go to bootcamp. I turned off the light again and it hasn't come on in 350 miles so far.

Now I have to worry about the water pump. It's starting to seize up because apparently the previous owner never changed the coolant. So far this truck has been more cost per mile than any car we've ever owned. 3,000 in six months with more problems showing up every day.

Rage469

Wow sorry to hear all of the issues you are having....I am a technician at a toyota dealership and can tell you that 99% of the time that code is automatically replace catalytic convertor. But in your case I would check the o2 sensors because that is really only other thing that could be bad. If you can get a scan tool that can show values such as voltage I would check what the o2 sensors are sending out. As far as modifying things so that a high flow cat can be used I am not really too keen on that as I am only allowed to do things by the book. My 4runner has over 200k and has zero issues but the exhaust is one thing I would not modify on my besides maybe a muffler. Water pump is maybe a 2hr job with decent tools. About 45-1hr with great tools.

SharpStick

Maybe you need to spend less time in big puddles.

Seriously - will excessive water submergence as in Rudy's avatar kill a catalytic? I can see that being harmful over the long term with corrosion and such, but can the underwater experience bring instant death?

STICK

4runnerteen

You know that is a good point. I think maybe some dirt and water got up to the cat and clogged it all to hell. And possibly the O2 sensor. take the sensor out and clean it. It might work then.