Service Engine Soon: Code P0171

Corsairprime

My problem was caused by fake Denso Iridium FXE24HR11 spark plugs. The electrodes on all of these fake plugs melted to a gap of .075 to .080. I did buy new plugs from NGK, the Laser Iridium DF8H-11B plugs and this fixed my issue. I also replaced the front O2 sensors in the midst of troubleshooting my troubles. I had rough and misfiring issues with the fake plugs. I checked and tightened the entire intake tract and secured all vacuum hosing with fresh clamps to eliminate and vacuum leaks. The fake plugs were confirmed by the fact that the writing could easily be scraped off. The real Denso plugs do not let the lettering scrape off, the letters are under the glaze on the insulator. The fake plug issue is widespread on the web.

Hope this can help you ID some of your issues. Best of luck.

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Corsairprime
2014 Nismo #462, GunMetal Grey, GT-R Start Button, AAM S-Line/R-Line intake and S-Line exhaust, Berk HFCs, Osiris Tuned at JoTech