2007 Lincoln Navigator flasing engine light and won't pass 80 miles per hour

You have a catalyst damaging misfire. This is a misfire that can ruin your catalytic converters. It may only be happening over 80 mph becuase of the amount of load the car is under at that speed. I would start by checking the condition of the spark plugs and fuel pressure. Do not drive much longer like this as it can cost a lot to replace the cats. Alex

SLOW DOWN!

Man,the NCSHP here in NC will get YARIS for going 80 mph! if you've been driving it with the CEL flashing for 4 days,the cats are most likely toast!