When the mass flow sensor was replaced, the check engine light was reset, and although the problem reoccurred, the check engine did not illuminate. Recently, just after refilling the gas tank, the check engine again came on. I immediately checked the gas cap, but it was secure. I took it to Checker Auto (free ODB scans), and their ODB scanner indicates a 1132/1152 oxygen sensor out of range.
However, the check engine decided to reset and went out while driving, but the vehicle is untrustworthy.
I guess the next stop is the dealer and $100 to diagnose.
BTW - I own a Jeep Cherokee with 365,000 miles on it and it has seen the dealer once. My Hummer H3 runs like a top and never lets me down. Unless I can resolve this problem, my wife says, it's the last Ford she'll own.
Chuck