So i bought a 2004 coupe and the seller did not provide a me with a smog and this being my first time buying a car, i did not know what to expect, all the paperwork needed etc....So i purchased it took the paperwork to the DMV and they told me i needed a smog. I took it to my local shop n it did not pass because the "check engine light" was on. I was getting code P1273 & P1283. I took it to a mechanic in daly city that my buddy knows and they told me to change my MAF sensor. So i did that and nothing so i took it to infiniti. They told me that the sensors were good but that my computer was acting up a little bit so they took it apart checked the wiring and placed it back. He said its working fine now so try to get it smogged asap. I took it to a shop my dad knows off and he asked to see the old smog paper and told me it would not pass since it has GROSS POLLUTER and is now in the system. He scanned the computer n said the the two codes were still pending, so he advised me to take it back to the infiniti. On the way home from there the Check engine light came back on and is now on...again.
So do you guys have any suggestions on what i can do?
Infiniti told me to change my exhaust since i dont have a y-pipe..could this be the cause?
Oh and when i purchased the vehicle it had a cold air intake, and Injen cat back exhaust. I changed the intake to stock changed the MAF, did an oil change but still have the exhaust on.
Anyone that can help plz do i greatly appreciate it

What are the codes for? I know I could look them up but I'm feeling particularly lazy about it today.

Bank 1 & 2 o2 sensors....running rich and lean.....and you can smell it sometimes even while im in the car

The O2 sensors needs replacement most likely (foremost importance in smog test). Cat converter also plays an important part (aftermarket cat doesn't do good on smog test for they're high flowing, ..for performance). Good thing you put back the stock intake, ..'cause after market intake will make the car run lean without adjusting the LTFT/STFT (tuning).

Stock spark plugs are good for smog test (stock heat range).

Do you think the previous owner tuned it with higher timing, adjusted LTFT (long term fuel trim)?

I had my 04 G35 coupe smog tested last 28th of April, 2011 here in Toronto, Canada and it passed with flying colors, all zeros on the results, it's stock though.

Also brought the car to the track for its first time 2 days later and did 14.489 @ 99.27 mph, completely stock. I forgot to lower rear tire air pressure..2.250 60 ft. I admit the G35 coupe stock needs more torque ..and hp.

I have never heard of LTFT so ill have to look into that and as for cats is there a way by just looking at them if they are high flow or not?....do you think i should change the senors even if dealer said they were all
good?

fyi i smogged it already but i would still like to fix it so that i can pass it in 2years, so if you guys have any suggestions that would be great

P1273 NISSAN - Air Fuel Ratio (A/F) Sensor 1 Lean Shift Monitoring Bank 1

P1283 NISSAN - Air Fuel Ratio (A/F) Sensor 1 Lean Shift Monitoring Bank 2


In tuning the PCM (gm cars), ECU (imports) the computer balances the right amount of fuel for every rpm, this is called the LTFT, and its value being perfect is "0". Anything from -3 to +3 LTFT is acceptable, on whatever throttle position you are at. -3 being rich (ECU is deducting fuel) and +3 being lean (ECU is adding fuel) to reach the proper air fuel ratio A/F ratio of 14.7:1 (not on boost, on less than 100 Kpa Manifold pressure). Once you're boosting, from 100 Kpa and up A/F ratio goes down, i.e. 13:1, 12:1 etc.

In my tuning experience with my previous car using DHP tuner/ data logger,( I've supercharged my 97 Pontiac Grand Prix with roots type, M90 s/c); Once I get to +7 LTFT I will trigger a lean code (SES light). With a tuner you could even disable a code (only on non-important codes) especially if you have an aggressive camshaft.

On the codes P1273 and P1283, sensor 1 is the primary O2 sensor, closest to the engine from the exhaust manifold. The sensor measures the O2 content on the exhaust to determine the right amount of fuel for the injectors to spray dictated on the ECU value A/F ratio, as per rpm and as per manifold pressure. In tuning the ECU, ..LTFT is adjusted by mapping the MAF (MAF values per rpm, from 0 rpm all the way to 12,000 rpm).

I say make sure that your ECU is stock and not tuned (tuned meaning values been changed in the MAF table and or timing/spark advance added) in the spark advance table. This is since you don't have mods like an intake, cam etc.

Did you say your exhaust setup is no longer stock (maybe it's just mufflers but not the cat converter). But check, the dealership should be able to compare a stock cat from aftermarket cat.

If they think the O2 sensor is okay, tell them to clear the codes first in the ECU. Drive your car and see if the codes comes back. If it comes back then you know the sensor is shot. Make sure also that the ECU is not reprogrammed by some tuner before, if it is, it has to be reflashed to stock. Make sure your intake is stock, stock air box, panel air filter. Hope it helps. Bin Laden is dead by the way..

Simple answer to this: The previous owner had the cats removed and has test pipes installed. You will get the codes you are throwing if you have test pipes and you will smell it outside of the car. If you do not have test pipes you will not smell exhaust. You will not pass smog with the test pipes so you will need to get them removed and OEM cats installed.

Alternatively you can reflash your ECU to remove the code or try and install 1 or 2 non foulers on each side. Search to find more information on these.

If there are no cats it will never pass emissions. Didn't the dealership or you (Lazybay) not noticed that there was no cats but instead some sort of big pipes. You'll see them from the sides of the engine just below.

Is this a Naturally Aspirated car with no cats? What is there to gain? 5 hp and the smell of rotten eggs..

I bet OEM cats of the G35 coupe is very expensive (there are 2 of them). Midas have 3 way cat converters for $75 ea. but it will need to be welded. My 3.8 lt. V-6 with an M90 S/C passed emissions with just one of these cheap Midas 3-way cat. Maybe a Magnaflow high flow cat might even work if you don't want the restrictive Midas cat.

Anyways, cat converters are going to cost you some..goodluck.

you need to look under the car and see if you have aftermarket cats, stock cats, or test pipes

the codes you have (sensor 1) are normally the upstream O2 sensors though and don't have anything to do with the cats. Normally means you just need to change your O2 sensors.

It has cats...the smog inspecter said it did, i can visually see them, and the dealership said the same thing...It could have test pipes as "canadian" said maybe it could have that and thats why i can smell it all the time...is there a way to tell what type of cats it has w/o havng to take them off?....dealer did check the sensors and ecu they said both were fine. he told me he even took the ecu out and inspected it...after about 50 miles the same code did come back on tho

Thanks for all the input guys i really appreciate it

Might just be bad/gutted cats. I never smelled any fumes when my exhaust was stock.

Gutted cats maybe?

I failed about 2 years ago. My cats were bad with no CEL. Replaced by infiniti under California Emissions law. If your car is under 8 yrs/80k, put as much as you can back to stock and try to get infiniti to replace them. OEM cats are super expensive and at the time no one made aftermarkets. IIRC they were $800 for both or maybe each. I got lucky.

Herrschaft-My exhaust isnt stock...Gutted cats possibly and Holy S*** thats a lot for just cats lol oh well i have two years to not worry about it since i got it smogged already lol

EDIt: Here is a pic
http://www.flickr.com/photos/42035460@N06/5711899729/http://www.flickr.com/photos/42035460@N06/5711899729/ by http://www.flickr.com/people/42035460@N06/, on Flickr

Are those extended bungs I see? Not sure why those are on, but remove them (at least for now). To reset these codes long enough to pass - you need to unplug the car from the battery for about 8 hours (overnight).

Buy or borrow a code scanner, drive about ~50 miles and scan and see if there are no codes pending. Depending on the setup - you basically have about 10 miles of driving between the time when the codes are ready and a fault will occur.

BTW, there are some epic part out threads in the private market place that will probably have an o2 sensor (if you suspect they are bad). Otherwise they are about $100 EACH.

p.s. do not limp drive the car, try to get the full range of your rpm or your codes will take forever to get ready.