RunnerUp

hey again, ive spent days searching for the answer but to no avail. i have a 2002 4runner that is a cali emissions model (i.e. 2 cats). my truck had been running rich for awhile and i guess between that and the seafoam my front cat has finally quit working properly.

my question is, can i get away with replacing the first cat with a high flow cat from magna flow and remove the second cat downstream with out setting off anymore check engine lights? i was just quoted 350 + labor to get the new cat assembly, and would like to spend alot less.

thanks yotatech

Shoretaco

Yes that is what I did. I live in NJ and passed with flying colors. You will need a high flow cat , then a test pipe with an 02 sensor in it and the some kind of muffler. I would look into that price of $350.00. A new cat is $100.00 plus a new muffler , and a test pipe. If you can weld your in good shape and can get er done cheaper. I could not weld and had it done for $260.00.

fullmann

from all of the reading i've done on the subject, anything but factory toyota cats will throw a CEL (probably p0420) on the cali emissions vehicles.

most fixes involve using some sort of o2 simulator. I personally think the simulator is a band-aid, but at this point, I am unwilling to dole out the $2k+ for a factory dual cat assembly.

If you do end up finding a replacement cat that doesnt throw a code, please let all of us know, I know I need one.

mt_goat

That has been my experience, one cat will not fool the ECU.

RunnerUp

so is the consensus so far that i need to shell out the 350+ labor or can i just get away with a high flow cat and a new location for the downstream o2 sensor?

fullmann

I think the high flow cat will work fine, and the engine will probably run good with it. but with the cali emissions, you WILL throw a p0420 cel, and i'd imagine the ecu will try and compinsate for that code. I have no idea what that will do specifically, but mine is getting 22 mpg and seems to run fine with that code/cel on right now.

I was told that these guys, http://www.empirepao.com/ make an O2 simulator, as well as urd has one too. if you decide to do the single cat, this should mask the cel.

Shoretaco

Like I said I have a single high flow cat from Lc engineering. I have a California model 2.7l. I removed the stock setup and installed a Lc header, high flow cat, test pipe with 02 sensor and new muffler for about a year. No issues and I passed inspection. Maybe I'm lucky but the 02 sensors read before and after the cat, why would 2 small cats be more efficient to one bigger hi flow cat. Just my 2 cents. You can buy the simulator after you get the code if you need it.

mt_goat

Maybe because you have a 4cyl, on my 3.4L with one Carsound (magnaflow) cat I got a P0420 every other day until I installed a URD O2 simulator.

Is your one cat bigger than the factory cats? All cats are high flow now, or so I'm told.

Shoretaco

The stock cat on a cali model up front is about 8inch wide a 10 inch long. It then travels about 24inches to a second smaller cat. I replaced with 2.5 inch lc cat in and out. No problems at all. The six cyl engine needs more of a cat I would say so It may not work. But I would try it and then add the Simulator later if it does not work.

mt_goat

Yeah I know what the stock cats look like, I have a set of them :


I think you have to think of the cat as a filter and I'm thinking 2 small filters will filter better than one big one. There must have been some reason the Toyota engineers went with 2 small cats instead of one big a$$ long one.

RunnerUp

alright, so would the better choice then be to just shell out the $$ for a new part (350$) or go to a new cheaper muffler and just get an O2 simulator from URD? i want my truck to run perfectly and im not sure how much i trust an O2 simulator

mt_goat

The O2 simulator doesn't effect how the engine runs because its for the rear O2 sensor, the real question is will you pass smog with it? (It is illegal for road use) In your state do they test the tail pipe emissions or just look for a CEL being thrown by the ECU?

BTW what does the muffler have to do with any of this discussion?

Shoretaco

If that is so, why didn't they make them standard on all models. It's probably mandatory in California to have 2 cats after a certain year. I think its overkill. If mine works without a code ,and its a little larger than the second cat ,who's to say its not as effecient as 2 smaller cats.

RunnerUp

florida doesnt smog test the vehicles, dont ask why, they just dont, so that part doesnt matter for me. what will be different about my tail pipe emissions if i use an O2 simulator?

i have no clue abt the muffler part of this discussion, and can we please not turn this thread into an argument over stupid stuff? i need to get a concrete answer on what is the cheapest way and also what is the best way to fix this without getting a recurring p0420 code

thanks guys

fullmann

the only thing that really bothers me about the o2 simulator, is if the rear o2 sensor actually has anything to do with how the ecu tunes the motor, or if it is there soley to check the effeciency of the cats.

if all the rear o2 does is check the cat(s), then I would have no worries using the simulator in conjunction with a regular high flow cat.

can anyone confirm or deny that the rear o2 is there for anything but checking the cat(s)?? or does it have anything to do with how the ecu tunes the engine??

i'd think the front o2 does all the tuning, but i've been wrong before.

mt_goat

So is your problem now that you're getting a P0420? If so, as long as your cats aren't clogged and you aren't worried about the smog police and you can handle some soldering and wiring, I'd just install the sim and leave the cats alone:
http://www.urdusa.com/product_info.p..._id=1230100014

The simulator will just fake the ECU into thinking the cats are working fine, it will not change emissions or anything else.

RunnerUp

ok... so how would i tell if my cat is clogged?

and would i gain anything by replacing both cats with high flow? or removing one cat and replacing the other with a high flow?

mt_goat

"On the truck" a good muffler shop can test the back pressure before and after the cat. A big difference means a clogged cat.

"Off the truck" as long as there isn't a curved section of pipe, you can tell just looking to see how much light you can see through the honey comb.

Again, as I understand it, ALL cats now days are high flow, so you already have high flow cats and putting on another high flow cat will only help emissions if your old cat is bad.

RunnerUp

okay, so one more question. i dont believe that i have any o2 sensors after the second cat, so could i not just cut that one off completely and get a new cat just to be safe for the front one and run the o2 simultaor?

mt_goat

What codes are being thrown now? If you don't have a rear O2 sensor in place you should be getting more than just a P0420. A working rear O2 sensor has to be in place for the URD sim to work.