NHTSA isn’t too happy with Ford’s response to the carbon monoxide problem. Welcome to the club.
Ford tested 4 Explorers, some that had been repaired using the steps recommended in TSBs, and didn’t find a problem:
“Ford says all these CO levels are well below any standards, especially since investigators found only “momentary” levels that quickly disappeared. In addition, when investigators allegedly drove the SUVs without using wide-open throttles, the carbon monoxide levels were zero.”
NHTSA took Ford’s “there’s nothing to see here” conclusion under advisement, and then promptly upgraded their investigation to an “engineering analysis.” They also expanded it to include the 2011-2017 Explorer, roughly 840,000 vehicles total.