Hi guys, I'm new this forum and I need some help.
I have an '05 F-150 FX4 5.4L with 48K miles. It was idling rough so I took it in for a tune up (I wasn't attempting those plugs after all the horror stories). After a $500 tune up with 2 new fuel injectors it is still idling rough and the mechanic says if it isn't throwing a code there is nothing he can do. He said coil packs are good. IAC valve maybe, but is there anyway to know for sure without buying the $60 part and swapping it out? Any ideas?

 

with the engine running wigle some wirers under the hood maybe the mas air flow sensor wirers, maybe o2 censor did they hook it up to a diagnostic machine? maybee the service engin soon light that tells you a code is being spit out is out just some ideas off the top of my head

 

Be sure to check for vacuum leaks. A quick shot of carb cleaner into the engine compartment will tell you if you've got one.

 

if you have underdrive pulleys and have not set your idle higher that would do it

 

The injectors on 05 5.4's are under extended warranty - you may still have some leakers.