Running lean
 

Hello all i recently got an 04 Z the "Service Engine Soon" light has come on i took it to the nissan dealership they tested it and said it pasted all the test properlly so there is no reason for the light to be on now they said but he showed me it was running like 12% extra fuel over the short trip so at some point the A/F was off. They suggested to replace an O2 sensor, not sure wheather thats what codes came up as issues or they just want me to spend money. My Z has some upgraded intake almost a cold air but not truly if the car is running lean i know that mean there is more air coming in and not enough fuel i want to make the most cost effective fix i think it could be any of these issues:
1- Dirty or Faulty O2 sensor
2-Faulty Mass Air Flow Sensor
3- Clogged fuel injectors
4- Leak in fuel system
5- Leak in exhaust system
What is wrong and how can i fix it?

Is my A/F actually off or are the sensors just broken and saying the mixture is off?

Rent an OBDII diagnostic tool from Autozone (it's free, just a refundable deposit). Then look up the code.

Welcome. Lean is pretty vague. Would like to see a air:fuel chart before fixing something which does not need to be fixed.

You can clean the MAF sensor.
Removing and cleaning the oxygen sensors is a headache.

NOTE: Nissan diagnostics may be telling the mechanic which bank is suspicious, but the mechanic is not giving you the information.

I will try renting the OBDII to see if it comes up with the same code indicating the O2 sensor, maybe that will narrow it down. What confused me is that the A/F wasnt off when they tested, but it was at some point should i reset the light and see if it comes back on? How can i get a A/F chart does the OBDII have this aswell?

"NOTE: Nissan diagnostics may be telling the mechanic which bank is suspicious, but the mechanic is not giving you the information" Your Exactly Right he flashed the papers to me and quickly hide them as he explained it.

i got an OBDII and it is p1273 air fuel ratio sensor how can i fix this?

replace the sensor

Is the sensor destroyed or is it just alerting me that its off i took it to the nissan dealership they ested it and sayd there is no reason the light should be on currently everything is on spec. Ihave an upgraded intake ever since putting it on the air fuel sensor goes off. should i get a fuel managment chip? have the sensor replaced? or just take it some where and have it tuned?

Get someone to check for vacuum leaks after the MAF. This is the most common cause of none AFR sensor related lean codes... Most likely not your intake unless unmetered air is getting in the engine. Check all obvious sources for vacuum leaks. (mainly unplugged or damaged vacuum lines.

im having the same problem
i drive an 06 with headers tp cat back intake pullys and spacer
it told me bank one sensor one and i had replaced it yesterday but the light came back on last night...you guys would clean the maf and then check for vaccume leaks...i've had everything done around may june and maybe a month ago this problem started

I tried Cleaning the MAF yasterday the light came back on shortly after reseting. I did notice that there was no heat shield on my short ram intake. Could that be throwing it off?
I dont want to do the same thing that NissanTech350 did spending all the money to replace a good part my car only has 45k mi they shouldnt go out till 80k plus so i think its something else throwing off my air/fuel sensor.
Can this vacume check be done at the dealership? approximatly how much would it cost?

I charge 2 hours labor ($89 an hour) at my shop for a "smoke test". If there is a vacuum leak it will generally throw a code for both banks unless the leak is on one or two particular plenum from the same bank or "side". What type of oxygen sensor did you use I have experienced some Bosch sensors that are not 100% compatible with their advertised application. I would have used a oem sensor I believe nissan uses denso. Most big dealers should have the proper equipment to do the test. The heat shield on the intake does not affect anything but intake air temperature which there is a sensor to measure that so that isn't hurting anything (technically it does hurt performance).

Bank 1 sensor one what? Lean, Rich, Slow Response, or heater circuit failure.
Which sensor did you use? Do you remember the exact DTC? If the MAF was the problem you normally get a code for that as well.

My issue is the Bank one sensor one P-1273 took it to the dealership they said it was running lean at some point thats why sensor went off so they tested it and it came back running in spec. said i should replace the sensor.car has only 45k mi so i figured it was something else to go wrong like the intake installation i recently had done before the light went off?

just listen to what people are saying and replace the sensor.

Just because most people get 80k out of the sensor doesn't mean that your sensor didn't go bad at 45k. Just replace it and be done with it. stuff breaks and it sucks.

Yeah **** happens... I've had my LR wheel bearing and hub assembly replaced at 15k miles and my window regulator replaced at 16k its all part of the car ownership experience. LOL These air/fuel sensors are alot more sensitive as well sense they tell the ecu exactly how rich or lean the car is running.

Im a total Noob when it comes to engine stuff on my car. I am having the SAME exact problem but my code is P1283, My question is where is the air/fuel sensor located? :confused:

http://www.nissanhelp.com/diy/obd_codes/p1283.htm

It's your oxygen sensors. They are the "air/fuel" sensor you seek. There are 4 on your car. One on each header, and one on each catalytic converter. They are as follows;

Left Header: Bank 1 Sensor 1
Left Catalytic Converter: Bank 1 Sensor 2
Right Header: Bank 2 Sensor 1
Right Catalytic Converter: Bank 2 Sensor 2

Narrow it down to which one is bad, and just have it replaced. Pulling it out just to clean it isn't worth the labor and headache. I'd just do all 4 sensors while you're at it because after one goes bad, another goes bad, and another, and another, and then another.

Omgosh.. The previous owner on this car told me he had done the ez CEL fix for his TPs. Where he covered the O2 sensor with a spark plug thing to lessen the amount of stuff getting to the TP. Do you think that could make the computer think the car is running lean??

+1, I had the same problem at 65K, I replaced the sensor and was done