I have a 1997 F150 XLT with 4.6L triton. I'm not sure why but when I come to a complete stop or I put the truck into park it will begin to hesitate. But it doesn't do this all the time and the hesitation changes each time. Sometimes it get will shimmy really bad and then just stop. Other times it will be just a slight hesitation and sometimes it won't hesitate at all. If anyone knows what this might be please let me know. I have already replaced all the minor things such as spark plugs, fuel filter, pcv valve, and air filter.

 

if she stumbles in park is suspect the i.a.c valve needs a cleaning. had similiar type symtoms on my 97 4.6 and it was the i.a.c

 

The next time it starts doing the stumble pop the hood and tap the IAC with a screwdriver handle to see it stops.