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2004sl 4/1/2010
2004 Nissan Maxima SL 6Cyl3.5L - Engine
Dear Auto MD, I require assistance in solving a frustrating problem with my engine.
My 2004 Nissan Maxima is running rich after the installation of a complete performance exhaust that included headers, a hi-flow cat, a resonator, and a catback. I also have a couple modification that did not contribute to the 1273 code as the code existed before the additional modifications were installed. My engine has been running rich for almost a year. I am getting an engine code (1273). I want to know what I can do to make my engine run more lean or even normal?

Thanks very much!

2 Answers
  • jondmn
    jondmn 4/1/2010
    Try replacing the oxygen sensor.
  • HouseCallAuto
    HouseCallAuto 4/1/2010
    Here is some similar posts and their fix -
    It would seem that you have either a bad air/fuel ratio sensor or you have an exhaust leak near the sensor or catalytic area.

    2004 Nissan Maxima 3.5L, USA/Canada

    Customer Concern: Code P1273. Changed the mass air flow sensor. The light is still on.
    Tests/Procedures: 1. Review the 3 Technical Service Bulletins that pertain to code P1273.

    2. Check for exhaust manifold/ Catalytic Converter cracks near the Air/Fuel Ratio Sensor
    Potential Causes: Air Fuel Ratio (AFR) Sensor
    Air-Fuel Ratio Sensor
    Cracked Catalytic Converter
    Cracked Exhaust Manifold

    Tech Tips: P1273 is for Bank one Air/Fuel Ratio Sensor (firewall side). Indicates a the Air/Fuel Ratio Sensor has shifted to lean for too long.
    Diagnostic Codes: P1273
    Author: Steve Wilson
    Average Reported Mileage: 94000

    Confirmed Fix Summary

    Confirmed Fix 1 - Air Fuel Ratio (AFR) Sensor, Spark Plug(s)
    1 - Catalytic Converter
    1 - Exhaust Manifold

    Confirmed Fix Details

    Tech Reported Fix Details Confirmed Fix
    March 10, 2008 2004 Infiniti G35, 3.5L, USA/Canada *
    Replaced Air Fuel Ratio (AFR) Sensor
    Replaced Spark Plug(s)
    - Random misfire code 300.Bank one running lean.Swicth air fuel ratio sensors side to side .Lean running fallowed the sensor.Replace the bad sensor and car is now 100%.Replaced plugs and checked coils on a scope and found nothing wrong. Air Fuel Ratio (AFR) Sensor, Spark Plug(s)
    Jay Brar
    October 12, 2009 2005 Nissan Quest, 3.5L *
    Replaced Catalytic Converter
    - heat shield spot welds on the convertor were leaking. heat shield was barely held on. Catalytic Converter
    Harold Williams
    January 31, 2008 2004 Nissan Maxima, 3.5L, USA/Canada
    Exhaust Manifold
    94,000 miles Exhaust Manifold

    2004sl 4/3/2010

    Your assistance is greatly appreciated. However, my oxygen sensors were inspected and checked OK and I did have a leak but it was repaired after my mechanic used a smoke machine to find the leak then he repaired it. That eliminates those two possibilities, but at this point I am still willing to try any additional suggestion. Kudos to you though because you have provided the best answers for my engine problems to date. THANK YOU!

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