I know this doesn't have anything to do with an FX4... but my '99 and '07 always shook at idle. When people get in my '07, they think they are riding in a diesel truck. Literally you can see the bug shield vibrate, to the seat belt buckles vibrating. However it is NORMAL for the V6 to idle like this. However, it doesn't vibrate like a revving little engine... it shakes like a big engine. So it's really not vibration sort of speak, but a shake, but when it goes through the frame it feels like a vibration. I guess that's a good explaination for it.

My V8 in my Dakota on the other hand actually swings the truck from side to side, like someone is rocking the boat. It's a weird feeling... it's even weirder when you rev it somewhat and the truck tips to the right about 1/2 inch. It's almost like there is an angry beast under the hood.

 

yea my 06 stx vibrates at idle,when i first bought it I took it back because of that,but they let me sit in a couple other new ones and they ran the same way,he said its just the way they idle for emmision reasons I guess.28k miles later it runs the same!

 

Mine idles rough too, but not all the time. Seems to get better when the engine is warm. But it's not always smooth when warm either, and A/C doesn't seem to make any difference.

I'm not overly concerned about it, but it's yet another aspect of my truck that was designed poorly, and these things are really starting to add up.

 

I read this on another ford truck site. It may be totally BS, but I tired it and it seems to have made a diffrence.
With engine hot and a/c off
1. Idle one minute
2. Turn on a/c and idle another minute
3. Turn off a/c and idle another minute
Maybe all BS, but it seems to have calmed down the ilde shakes on mine
2006 5.4

 

Double Post

 

Mine used to have trouble and stumble on itself when u "blip" the throttle it used to some times die and idle would drop low and come back up slowly... I took off the throttle body and cleaned it, also changed the fuel filter, and raised the idle by 15 on my edge and it works great now

 

JstabFX4 - Check your tailgate latches for that squeak. That's what it was on mine. Drove me insane and I thought it was my suspension or rear-end. Lubed up the tailgate latches with some dry lubricant and it stopped.