PO171 error message

[yardmech]

I have a 2000 Nissan Sentra with the 1.8 liter engine. I keep having the PO171 error code coming on. I have replaced all 4 O2 sensors, the temp sesor and all plugs. What else should I check or replace.

[boriquaS13]

I believe that a po171 is a lean condition check your mass air flow meter and see if its contaminated and clean it off clear the codes and drive it, also check for any vacuum leaks this would also cause your problem.