Just started a few days ago. It's a 2007 Supercrew 4.6 with 42,000 miles. When you are stopped at a light it idles rough then smooth in succinct intervals. Maybe 10 seconds of rough idle, then 10 seconds of smooth. Not bad gas because it's done it for 2 tanks now. No mods on the truck and always do the regular maintenance. Anyone know what this could be before I take it in to the dealer? Thanks.

 

My 2008 4.6l runs rough when first started, sounds similar. Smooths out after driving for a while 2300 miles.

Jerry

 

Maybe a vacum leak but that wouldn't really make sense because it should do it all the time.

 

Mine did the same thing, it needs the throttle body cleaned. The throttle body gets very dirty very quickly and the 4.6 seems pretty sensitive to this. Also clean your MAF really well also. These 2 things really smoothed out my idle issues

 

Also replace the fuel filter if you have not already, it gets overlooked at times when having the regular maintenance done