heavychevy

Ok I've researched quite a bit and am trying to come to a final decision about what to do with my exhaust. I've got a 03 federal spec max. I believe its got three o2 sensors. Everyone talks about gutting the cats. Mine had 152000 on it and I don't know if their broken apart inside or clogged or fine. The exhaust is still quiet no leaks. I'm wondering if there will be any performance gain with doing this.Ive heard many opinions of the cats breaking up and damaging engine and I'm not sure if its true or was more on the altima than maxima. Any thoughts or ideas would be appreciated

NmexMAX

iTrader: (22)

Gutting cats will give a slight performance gain. And you have 4 sensors, 2 per bank, a main and a secondary.

The idea has been thrown around here often enough to think it might be a legitimate problem, (cats being sucked bakc into the engine). But if you;re car isn't burning oil, it should be fine, and if you're not throwing any cat codes, likewise and it should be fine.

nsnrider

iTrader: (59)

it is only a matter of time until you get the dreaded p0420 p0430 codes code catalytic converter efficiency. With that many miles on the car, I am surprised the cats have not given you problems. You can wait until you get the CEL for the cats that way you will get everything out of your cats. When they fail, then you can change them.

you'll get slightly more horsepower with cat delete and a deeper exhaust note.

ACee

Headers!

NmexMAX

iTrader: (22)

Considering the PITA of removing cats at this age in the vehicles life, unless it's low miles and not rusted, it's probably better to invest in some cheaper headers, such as OBX if you don't feel like spending the $$ on more expensive ones.

Or there's always the aftermarket Bosal or other brand name pre-cat replacement.

Then again, gutting can still be done for cheaper and possible easier.

Mules5555

I have had gutted cats and no third cat for going on 3 years now and haven't got a code. Am I just lucky?

heavychevy

I thought Cali Max's had four sensors and fed or Canada had three. But I believe you being you have posted like 30000 times. Btw the car has one tiny spot of rust thats it I'm planning on keeping it I just bought it don't even have it on the road I just don't wanna make anything worse

02whitemaximase

iTrader: (38)

You are probably thinking of the 2000-2001 Maxima with the 3.0. All 02-03 Maximas with the 3.5 have 4 sensors.

NmexMAX

iTrader: (22)

Cali spec

Prophecy99

iTrader: (1)

sorry to hijack, thinking of this the other day but is it me or is the header LTB-StageII fitment conflict debunked? or was it one brand that didn't fit and rest do?

heavychevy

I've had the car on the road for about. Year and the 90420 code is always on.it is an oil burner and one of the cylinders tested 140 psi right at the minimum as per the Haynes book. So do I gut and 02 simulate or spark plug non foulers?

Dlowe90

I am in the process of removing my wife's cats, broke a few bolts (its got 140k miles on it) between the cat and the header. I see y'all suggesting just replacing the manifold with the cat.

my questions is this: If I can't get the cat separated, and I need to change the manifold with it....how likely is it for the bolts that attach the manifold to the block to be completely rusted? If i decide to just replace the manifold, is there a good chance the bolts will break or should I be ok?

WTF?

If you are considering it now, start spraying with PB blaster or whichever you prefer.....Be patient.....they will come.

Dlowe90

Thats the annoying part. I have been spraying it for a week and I broke one today. I undid all the bolts just a bit (felt more like twisting off the heads than actually loosening the bolts) and sprayed them more before I try again tomorrow. We'll see what happens tomorrow!

Mattx

iTrader: (2)

Do yourself a big favor. Instead of putting the socket on and hulking down on it right away like he man. Try tightening it first just enough to feel it move then even pressure, and as straight as you can loosen. It is the proper technique for loosening a stubborn bolt or nut.

Dlowe90

Interesting, will definitely try that today? If the bolts don't come out without breaking though, what are my options? Can i leave the heat shield off and be alright or am I gonna buy a new manifold in order to be able to have a heat shield?

Aserath

Cross posting this because this thread seems relevant to my issue.

I've had the p0420 code forever but with smog testing coming up decided to put in an o2 spacer. After resetting the code I've been trying to do the drive cycle to get the car ready for testing.

Today on the freeway car was driving great, went about 5-7 minutes, got off then back on the freeway the other direction.

Car accelerated fine, then at cruising (about 60) the car started struggling, the car still kept at speed but it felt like the car was going to die.

Got off freeway, drove surface streets back home and the car seemed to be absolutely fine. This isn't the first time this has happened, and it really only occasionally happens on the freeway.

Could an occasional problem like this stem from a bad pre-cat? It's just so strange that it only happens occasionally in certain circumstances. I'm at my wits end with this. I'm thinking about gutting the back pre-cat since I'm getting the p0420 and I do get occasional rattling when backing off acceleration in the 20-40 mph range.

What else could this be? I'd do the headers thing but I'm not planning on keeping the car. I also don't want to sell the car with this hesitation issue.

Thanks!

p.s. this is a 2002 Maxima

george__

iTrader: (1)

^
Get some new o2 sensors or used ones at the junkyard.

Gas cap

foodmanry

iTrader: (15)

Did you add the spacer in the primary or secondary O2 sensor? The primary is the sensor BEFORE the cat which controls your air/fuel ratio and the secondary sensor is AFTER the cat for emission purposes only.

Sounds like you installed the spacer in the primary O2 sensor position...

Aserath

I installed it on bank 1 sensor 2, the rear one that has to do with p0420.

This also happened prior to the installation of the spacer, which is downstream and should have no effect on how the car drives. That error code has not returned yet either.

I just provided that information to let everyone know what I've done.

The car is an oil burner, but my gas mileage has been fine.

foodmanry

iTrader: (15)

If it is hesitating you should look for bad ignition coil and/or spark plug. You can have a bad ignition coil and/or spark plug and no engine codes are shown. The ignition coil can also be intermittant.

There is an "ignition coil test" that you can try with a multimeter to see if you can find a bad ignition coil.

If you have a bad pre-cat that is clogged you will see it having a tough time pulling pretty much throughout your drive, all the time.

Aserath

Thanks for the suggestion I will check it out!

Aserath

After researching the ignition coils and what it'll take to check them I do have another question.

It seems to me if it IS a faulty coil it's only failing occasionally at high temps. If it's one of the rear coils how would you test that at operating temps since you have to remove so much to get to them?

foodmanry

iTrader: (15)

Ah yes you have an 02...crappy design for changing plugs and what not. You should start with your front coils and test. If you can't find the issue consider changing your rear three coils and spark plugs since you have to take so much part to get to them.

Any idea when the ignition coils were last changed?

Aserath

No, only bought the car about a year and a half ago. Actually bought a 2015 Honda Fit and am trying to get this car ready to sell. I don't however want to sell it with a problem like this, doesn't feel right!

I've already had to replace the radiator, tires, brakes/rotors/calipers. (Front caliper was sticking) Hesitant on spending too much more money!

Car really drives great otherwise, it's really annoying how intermittent this problem is, I've had it at a mechanic twice and they've driven all over hell and back trying to recreate the problem with no success.

Thanks for the help, I'm definitely going to at least check the front coils.

I read somewhere else on this forum someone recommending to "try closing up your sparkplug gap to about .028. Decreasing the gap lowers the voltage required to make a spark, which decreases the possibility of insulation breakdown due to insufficient standoff voltage at the higher voltage levels. Give it a try before buying new coils."

What do you think about that idea?

foodmanry

iTrader: (15)

No, don't modify your spark plug gap. The engine is designed with the proper gap in mind. Modifying it can cause damage.

If you are selling the car that's up to you, but as you said how would you feel about selling a car that has been modified where it creates engine damage?

Mateen995

or you can take a hit on the price that you let the car go for and explain the problem to the potential buyer if you already have a new car...

there is bound to be someone who will be willing to tinker with the car to figure it out, at the right price of course

Aserath

Does anyone think this could be a fuel pump or clogged fuel filter could be the culprit? The fuel pump was replaced right before we bought the car but the gas gauge in the car is inaccurate once it hits half a tank or lower.

Drove the car on the freeway last night in cooler temps and the car was totally fine. This only seems to happen when its hot out and at freeway speeds and even then not every time.

Thanks guys!

foodmanry

iTrader: (15)

If it was it wouldn't be intermittent.

Vince666

What year is your maxima? I have a 2000 with the 3.0 thought bout cutting them all out and straight piping them but people keep telling me I can't with these cars?

foodmanry

iTrader: (15)

You can, but you will need to install O2 sims or install an O2 spacer to prevent any SES codes.

That other guys SES light is probably burned out...for sure he has SES codes unless he installed O2 sims or spacers.

Vince666

I would definitely put spacers in it either way so I didnt have an exaust leak. But it looks like there's 3 cats? Is there a pre cat and two regular cats? That's what it looks like

foodmanry

iTrader: (15)

Well I don't know how the spacer would help with an exhaust leak. You can get bungs just to plug the holes if you want and run O2 simulators.

At any rate...yes, there are two pre-cats and one main cat. The O2 spacers or simulators would be for the O2 sensors located AFTER the pre-cats, or the secondary O2 sensors.

Vince666

I was wondering cause my main goal is to eventually run headers with 2 1/2-3" exaust all the way back straight pipe to muffler just haven't figured out yet what the best headers are and what size pipe would be best. I do not plan to run a turbo at the moment just pure engine. Otherwise it would be easy to assume go right to 3. What do u guys think? Also what's a great sounding muffler to run on these?

2000-Maxima-Guy

Got a 2000 Maxima GXE, 150K miles.

I got a CEL on the drive back from Oregon to California on Interstate 5 (near the border, in the mountainous area). This was back in Feb of this year (2015). Went to PepBoys, got a P0420 code, bank 1 front. Could have been cat, but guy told me was likely O2. Wouldn't know unless they ran the full diagnostic as opposed to using just the code reader. However, I decided to hold off and the CEL strangely went off by itself in two weeks.

But just last weekend, I took a trip to Yosemite & the light came back. Maybe this has something to do with driving in higher elevations? Anyway, I took it to my long-time mechanic. Got another P0420; he tells me cat needs to be replaced. And to do it right, should replace the O2's as well (had two of them in the back replaced years prior). I didn't replace them all when I had the chance. But did have all the sparks and coils replaced at around 100K.

Now I'm thinking I should have just done the O2 sensors first, just to see what the result would've been...? Maybe that would have been enough to make the code disappear. Plus I don't have a smog check until Aug 2016. But I decided on the $1200 repair anyway. Perhaps the wrong move, but I do want to keep this car another 100K miles. So...

Any opinions, recommendations, thoughts are welcome.

foodmanry

iTrader: (15)

If you have a smog check guy who doesn't "thoroughly inspect" you can install a spacer on front secondary O2 sensor and be done with it. The only problem is you won't pass a visual inspection during smog if they look thoroughly....

I'm in the same bot as you with a P0420. I had changed out my front precat 2 times and O2 sensor for I don't know how many times. I finally just installed an O2 spacer to be done with it. Luckily I have a smog check guy who doesn't look too hard.

Prophecy99

iTrader: (1)

i am not sure if I feel that ! and i almost feel a slight loss of low end throttle response

and i was at 184k and the precats were fine intact 100%