I have had my f-150 Triton V8 to a mechanic and have hade a tune up and transmission work done. The truck is still missing between 42-50 mph. The mechanic thinks it is a coil but no codes are coming up. Any ideas?

 

Welcome to the forum

Is the miss the same as before the tune up?
Your local dealer will have the scan tool needed to do a cylinder power balance test on the road to see which cylinder(s) is misfiring. Most other shops don't have the capability to do that.
Otherwise unless a misfire code happens you're pretty much shooting in the dark.

 

The miss is not as bad as before the tune-up. It happens at the same mph but not as bad and less often.