Recently bought an 04 G35 coupe from a private dealer in January with 56k miles. The day after I bought it I get a SES light with code 1273 and p1284 I took it to the closest dealership (Nissan) and they diagnosed it as a bad 02 sensor. Took it to the only infiniti dealership in town for the service and paid $500 for a new upstream o2 sensor. The problem continued and ended up replacing the other upstream sensor also. The problem continues so I called the dealership I bought it from and even though I bought the car “ as is” they helped out and replaced the downstream 02 sensors with non OEM sensors (is this my issue?). Problem continues. Took it back to infiniti and they told me I had multiple leaks along my exhaust. They replaced all the gaskets all throughout my vehicle including the headers. They also replaced my aftermarket intake because it had a small leak. They did a full compression test and tested for any vacuum leaks. Each time they tweak with the vehicle I am asked to come pick it up and drive it around town to see if the codes come back. Each time the code has come back within 60 miles of driving. The last visit they went through my ecu wiring harness and found some loose connections/ dirty pins. They cleaned and reconnected the harness and said the car should be fixed. I picked it up after they drove it nearly 100 miles to see if the light comes back. I was able to get the car to nearly 200 miles before the light came back on this time. I still have codes 1273 and 1284. Why is my car running lean in one bank and rich in the other? Could a non oem o2 cause this? They also asked if my vehicle was tuned but I have no records, I was about to take it to a tuner and see if they can see if it was tuned at one time. Out of options and Infiniti is wasting my time. Please help

edit: forgot to mention they found leaking fuel injectors on each side so I replaced every fuel injector with oem ones.

 

P1273 is lean bank1
P1284 is rich bank2

These are both generic codes, what tool are you using to scan for codes because it probably doesn't have protocol ISO 9141-2 which is needed to read the ACTUAL SPECIFIC codes the car is throwing. Neither of those codes is an O2 sensor malfunction so not sure why they immediately jumped to replacing your sensors.

Your downstream sensors are for catalyst efficiency, running lean/rich is measured by your upstream sensors in the headers. Exhaust leaks can DEFINITELY cause this though if the leak is the head-to-header manifold gasket. Which one did they replace are you SURE they did the upper headers gasket? Look through your paperwork and see if you were sold two part number 14036-AG010.

Regardless, lean on one bank and rich on the other with all those components that you listed already replaced makes me think you've got some kind of fuel delivery issue, probably a lot of sediment on the strainer/filter baggy that's on the end of the fuel pump.

If it is just a fueling issue getting the vehicle tuned can fix this since they will add/subtract fuel from the map as needed to get you back into spec.

EDIT: Nevermind you did say 2004 coupe.

 

Thank you for the quick reply, I am at work right now but I will check the paperwork when I get home. Infiniti told me they replaced all gaskets by the muffler/ cat and the headers. They provided a video clip of the leak as well.

I bought a Autel auto link code reader off of Amazon to save me a trip to autozone every week. I pulled them as Nissan codes so there could be a different code my card is actually throwing. I will call the dealer for the codes they pulled.

There seems to have been multiple issues with this vehicle that the dealer did not disclose to me, and most have been resolved by now. It is just trying to figure out why I still have the codes. I am not the ignore it type and I need this light to be gone before I feel my car is safe to drive. It doesn’t seem to idle poorly and drives smoothly.

There is small rattle I hear that comes and goes. If I am driving slowly in first and early shift to second I will sometimes hear a rattle/ clank type noise when I give it gas but the engine is bogged down a little. I had infiniti check the heat shield but they said it was fine? Not sure if this has anything to do with this code. There also seems to be a slight belt type noise when I cold start but I just had a serpentine belt replaced.

All in all I plan on getting my car tuned. I don’t have any mods except for a Greddy muffler. I would like to add a CAI and plenum before the tune. Why would getting my G tuned fix the issue? If the car IS tuned already and the previous owner had uninstalled some mods before selling it would this cause the issue?
I have called the only two dyno shops in portland that can work on a G and one is booked until June. A diagnostics alone is a week or two out.

As for the dirty oil filter, is that a project an amateur could clean?

I really appreciate the help, thank you

 

Call English Racing, they're up just east of Vancouver, can't remember the name of the town they're actually in. They mostly specialize in GTR's but they would almost definitely know who else in town can get you an UpRev tune.

Yes if the vehicle was tuned for a different setup that could definitely cause a problem.

You should see just how far out your fuel trims are, if your scanner can read short term fuel trim (stft) and long term fuel trim (ltft) that would be handy. Those codes are thrown because the LTFT is off by more than +/- 25% (pretty sure that's the cutoff for the CEL). The engine still has a lot of room for fuel management beyond 25% but it turns on the light so you know there's a problem.

If your engine is bogging when you give it throttle that's almost definitely a vacuum leak, go through all the vacuum lines yourself, intake pipe by the throttle body to the valve cover directly below the throttle body, front of the two valve covers is another line, pcv valve on the right valve cover to the middle of the intake plenum. There is a brake booster line that goes from the right side of the plenum into the battery box area, then it's a metal pipe across the back of the firewall, transitions again to rubber at the brake booster.

If you can turn any of those hoses by hand they need a better clamp. There is also a plug in the intake plenum near where the PCV line goes in, make sure it's tight and not ripped.

If the engine isn't bogging (sort of hard to understand what you were describing) and you only hear a "clank" when you give it gas at low rpm try to determine where the sound is coming from, if it's from the rear of the car it's probably the rear differential bushing, if it's from right around your gas pedal-ish it's probably the factory DMFW is seriously worn and the center/floating section is slapping around due to worn out springs.

Also double-check the intake tube for any rips, cracks, etc.

Lastly clean the MAF with spray MAF cleaner.

What's the issue with the dirty oil filter? Didn't see you mention anything about this in the original post.

 

I called English racing in Camas but they don’t work on G’s.. only PRE racing and VIP performance are willing but booking is far out.

Sorry for not being more specific about the noise. The dealer has checked for vacuum leaks and the engine does not bogg down. It is more of a rattle/ clank so I will read other threads and try to narrow it down but I don’t think this is related to my immediate issue.

You said “sediment on the strainer/filter baggy that's on the end of the fuel pump.” Sorry I couldn’t remember which part you referred to exactly when I was replying. Is this something that you can clean or just need to replace? How difficult is this to do?

I will see if my reader is able to monitor the fuel trims this evening.

 

Remove the rear seat cushion, two little pull tabs you pull towards the front of the car (they are at the front of the seat cushion down near the carpet). Next lift the cushion up and pull forward, this is how you access the fuel pump.

Disconnect the harness, the fuel line (strongly recommend disconnecting the harness then start the car and let it stall out from no fuel, this takes pressure off the fuel line), then unbolt the flange to the pump and lift straight up.

Be careful of the fuel level, you have to wiggle it around a bit to get the pump all the way out.

Be sure to have a towel or dozen laid in the car so you don't get fuel on the interior, strainer baggy is at the bottom of the pump.

 

Perfect, I watched a video and it looks a lot easier than i thought. I’ll see if there is a bunch of sediment clogging it and will also go buy some MAF cleaner and do that as well. I’ll see what infiniti says Wednesday when my advisor is back.

 

By rattle, do you mean coming from the engine? Like pinging? That would definitely signify a lean condition. Could also be heat shields rattling as you accelerate.

 

No it does not sound like a ping. It sounds like a rattle like something is loose underneath the car but it is hard for me to pinpoint exactly where.

I took a reading off my car last night. I’m not sure if I did it properly. I just plugged in my code reader and started the car. I found the readings for fuel trims.

At idle:
shrtft1- varied between 4.7% and 7.8%
longft1- 9.4%
shrtft2- varied between -2.3% and -3.1%
Longft2- 9.4%

Then I gave the engine a small amount of gas and the reading were:
shrtft1- went as low as -12.5%
Longft1- varied between 9.4% and 7%
shrtft2- as low as -18.8%
longft2- 9.4%

Do I need to drive around while logging this?

 

The dealership I bought it from replaced the downstream o2 sensors with non oem ones. The dealership is going to swap those out with the originals and only charge me if the SES light stays off. Is this a common issue for non oem sensors to trigger my SES light to come on?

 

No it's not a common problem, usually you can buy cheap brand O2 sensors and they work fine, they just don't last as long as good brand ones.

Your STFT and LTFT really should be tested while the vehicle is actually driven. Turn on logging, make a couple good pulls in each gear, go through the data and look for any super extreme data.

 

Hey guys just an update. So the private dealership I bought the car from installed non oem downstream o2 sensors. After replacing the 2 upstream, checking for all exhaust/ vacuum leaks, all fuel injectors have been replaced along with Infiniti checking through my ECU harness for loose connections. Drove it 200 miles and the light came back with ONLY code P1273. Infiniti replaced the downstream o2 sensors with oem and I have driven 220 miles with no code returning. I will update this if the code reappears. Thank you.