I have two codes going, system too lean bank 1 and 2. I have replaced my two heated o2 sensors, my mfa sensor. My intake is clean. I have checked the connection of my injectors. I dont have any exhaust leaks. I have looked up the other possibilities too, I just would like to hear from some other fellow nissan guys

 

Unmeasured air. Only three vacuum hoses to check, then inspect for cracks in your (plastic) intake components.

What are the codes? Does it run smooth or rough? What are your fuel trims? If you did work and/or replaced parts already and it runs fine, either clear the codes manually and wait for them to present themselves again or wait the requisite drive cycles for them to clear themselves.

 

So my codes are p0174 and p0171. I have cleared them both and then they came back on. It runs very smooth. Not rough at all. I do not know what fuel trims are, I'll look that up.my intake is aftermarket. It's a cold air intake by hps. I know there is no leaks, I've checked.

 

Run a can of Seafoam through 1/2 tank of gas.

 

If you have aftermarket bolt-ons and people have been monkeying around in there with that kind of stuff then it's going to be hard to say. Get the FSM and follow the work flow.

 

It sounds like a major vacuum leak to me. Tough to find if your new to them and the car runs well.