missing ,bucking at speeds between 40-50mpg
Changed out all plugs & two coils in my 1999 5.4 and now it's only missing when in fourth gear at speed's from 40-50 mph.
Before that it was missing in all gears.
It runs smoth at speeds over 55mph,around town I have to keep it in over drive so it will not buck.
I pulled the super chip and cleaned both computer and the chip,I thought I had it fixed but only lasted 20 miles.
I had the chip since new,do they go bad.
What else can I check.