I have a 97 F150 4.6. The truck has developed a slight stumble/missfire when under acceleration. Once at speed it runs fine. It has not given any codes. I've checked for them several times. The plugs and wires have been changed. Is it possable that a coil pack could be bad without throwing a code?

 

I would clean the mass air flow sensor and go from there
good luck and keep us posted

 

yes, coils can have a miss fire and not be bad enough to setoff a code. Sometimes goosing the throttle and playing around a little will make it eventually setoff.

 

Use a scanner in Mode $06 to look at the misfire counts to see which cylinder(s) are causing the problem, then troubleshoot. Otherwise, throw a coil at it and see if it sticks.