Originally posted by lkinley:
The MAF is probably fine.
I second that. In my experience, an O2 sensor is far more likely to fail. Plus, a failed MAF sensor would impact both cylinder banks, not just Bank 1 (I forgot to check if you have a V6).
I remedied P1131 purely by replacing the Bank 1 upstream sensor. It's somewhat of a pain to get to on the Duratec, but more than one CEG'er has done it successfully.
Good Luck!
