1992maximase30

well there's been this rattling noise sometimes at idle.
found out what it is.
it's the cat it's broken all up inside.

so i have to codes pertaining to egr and evap.
but no "cat" codes.

upon further inspection it looks as if it has pre cats for each bank.
which is why i'm thinking thats why there's no codes for it.

what i'm thinking about doing is getting rid of the precats and replacing the big cat.

or vice versa. what do you suggest?

eFLO

iTrader: (2)

get an aftermarket y pipe(warpspeed) and a new cat converter(if necessary) enjoy the power increase!

Conrad283

iTrader: (2)

The rattling might not be the cat.

It could be that the metal shield around the cat is loose and it's rattling. Chances are, if the cat were busted, you'd have a CEL.

The cat is expensive to replace especially if it doesn't need to be replaced.

If you want to do away with the precats, then get a y-pipe, as mentioned above.

internetautomar

iTrader: (30)

cats are cheap to replace around here, $50 installed is not unusual.
don't recall 97 having precats though.

schmellyfart

iTrader: (46)

They have 1 precat in the stock y pipe

ThreePointO

iTrader: (3)

thers is 1 precat right after each exhaust manifold in the y pipe and then one main one right after the y pipe. ur best bet is to just buy the kit from warpspeed.

Your cat could b the problem and you might not get any codes. I have a test pipe right now and my cel is off for months at a time and then comes back on for a couple of weeks then its off again. I have a 97 too.

92gxe/cg2

iTrader: (2)

The rear o2 is pretty much useless...monitors the efficiency of the cat, so if u get a code for it nothing else changes, the car will act as normal. The upstream o2 sensors are what matter, and replacing the pre cats shouldnt cause any problems or CELs there.

Not to threadjack, but ive been getting the code for the rear o2 off and on for a few months...i dont really have the money to buy another sensor or simulator but i was wondering, if i could just bypass it with a resistor. I tried searching for anything like this but couldnt find it. The ecu looks for a 0-1V signal back from the sensor, and sends out a constant 5V signal ( i thought), so if put an inline resistor in place between the 5v line and o2 output line could i cut the 5v down enough to "fool" the computer enough to get rid of my CEL or is this just wishful thinking?

Nismo32

did you check the flex pipe as well?? my car rattles when it idles and its because there is a crack on my flex pipe. no code will be likely that or one of the hinges is loose i have major rattle down under (no jokes on that statement lol it sounds funny lol)

1992maximase30

thanks guys. but i wish it was'nt the cat.
but it is.
soo i'm better off with a y-pipe instead huh?
well i guess so.
and this car has two of em.

my dad's 4th gen has no precats.
there has'nt been any work done to them either.

everytime i see a 4th gen come in the yard some have precats some don't.
majority of em don't have them.

and kevin puttin a resistor inline of the o2 is'nt gonna prevent the cel from coming on.
eithere get a new sensor or an o2 simulator.

VQ30DEMaxima

I have a warspeed Y pipe and I love it!! Installation was super easy, and then just get a test pipe dont worry about cats lol!!

Car With No Name

I just replaced my cat due to the guts having fallen apart...once removed you could see the honeycomb was loose and angled. The rattling was super annoying at idle so I had to replace it. I went directly through Random Technologies and was helped out tons by Clay (THANKS CLAY!). The RT cat is a nice piece to add to your exhaust.

92gxe/cg2

iTrader: (2)

Some dont have pre cats? I thought all 4th gens had them too... hmm..
Do you still need the 3rd cat to pass emissions stillman? Even tho they just hook up to the ecu dont they check to see if you have a cat?

Thanks stillman, but how come it wont work, because it will be a constant voltage back to the ecu instead of a fluctuating voltage?

bamboomerang

iTrader: (14)

Either way you dice it, replace the main cat, unclog your EGR tube, check out the evap system (goodluck hopefully it's just a faulty gas cap). Get code free first, then get a y-pipe if you want the extra horses.

For the record, the rear downstream O2 sensor technically does not affect the ECM, but it can throw off the knock sensor/timing advance, leading to a perceived loss of power and slightly more fuel consumption.

1992maximase30

well...the egr code say's low flow or none at all.
at idle you can here something that sounds like a straw trying to suck whats left at the bottom of a milkshake...mm milkshake.
so i'm assuming the diaphram is broken.

the evap code has something to do with a solenoid in the canister in the back of the car.
this solenoid is rarely used, but the ecu uses it to check the system anyway.

someone at work said maybe my ecu can only hold 2 codes...HA!! if the 3rd gen can hold some codes i'm sure the 4th gen hold hold quite a bit.

so the pre cats are doing the job.

it amazes me that with 170k, with all this resitriction this car moves!!
and that y-pipe i've heard thats the best bang for the buck if you want extra hp.


kevin. i think the 4th o2 sensors uses and on off type signal.
thats what i remember with my a/f gauge it would bouce back and forth between lean/rich.
until 3k rpms.

vq30demaxima:
if that was the case then i would get rid of the cat.
but i think they only do the pulg in type emissions here.

internetautomar

iTrader: (30)

any narrow band o2 sensor just bounces back and forth between rich and lean when viewed on an a/f gauge.

Illinois is only a computer scan.

92gxe/cg2

iTrader: (2)

yeah its like a sine wave continuously fluctuating, is that why i cant just use a resistor to get the voltage the ecu sees to seem correct? Brian you got any ideas?

internetautomar

iTrader: (30)

correct it is a wave pattern, a resistor would just be flat which the computer would interpret as a bad o2.

the rear o2 is there to make sure what is coming out of the cat is cleaner than what went in. only fix is to do it right, sensor is fairly cheap though.

92gxe/cg2

iTrader: (2)

Yeah i read up in the fsm on the sensor and found it was just for cat efficiency so i wanted to see if i could cheaply fix it. i saw the sensor for like 50-75? Is that what you meant by cheap? Its not bad but i dont see me shelling out that for the o2 anytime soon. Anyway the codes been off for almost a week now..

internetautomar

iTrader: (30)

yes that is cheap. you just better hope the code is off when it's time for license plate renewal too.
I don't have to worry about that though :P

1992maximase30

^^of course you don't.
and kevin an o2 sensor is something i would'nt wanna cheap out on or put a band aid on.
just buy the sensor.

1992maximase30

a friend of mine made a suggestion.
he has an 03 (i think) acura rsx.
no cat.
what he did was for the rear o2 sensor he put a washer inplace that way the tip of the sensor would get a reading but not enough to realizon't have a cat or the cat is bad.
think this'll work for the maxima?

internetautomar

iTrader: (30)

spark plug anti-fouler is the same concept. all it is doing is creating a slightly cleaner reading on the output side of the cat

1992maximase30

hmm...so you think she'll pass with this set-up and being completly catless?

internetautomar

iTrader: (30)

depends on if the CEL is off and the monitors showing ready.