I have scoured every form trying to diagnose my 2005 5.4L f150s reoccurring shake and every one is close but not the same as most. It only does it every now and then at HIGHER idle not low. It NEVER stalls or seems like it wants to stall. The common situation is driving between 50 - 70 mph and its fine and i go to pass or gun it and the truck starts to shake and the engine light flashes does this for about 30 seconds and goes away. Only does it in that situation. Never stalls, never does it at idle, only at high revs and seems like mostly in passing gear. Ive scanned it many time to read p0174 (Sys too lean bank 2) and p0303 (Cyl 3 misfire)

What ive done:
Changed the plugs and coils
threw a cat code once so i hollowed out the cats

Every time i look up a fix its always people with low idle and stall issues or cam phaser ticks which mine never does. it runs fine other then that bad shake and loss of power at higher rpms now and then. Anyone have any ideas?

UPDATE: Cleared the codes and ran it again and it threw a p0308 (Cyl 8 misfire) so the cyl misfire is dancing around

 

How about the fuel filter?

 

Checked it seems okay. i guess it could be the pump tho but how would you check?

 

Just replace it. Even if it's not the problem it's a good idea to change them occasionally. Watch video on YouTube. May take a special tool.

 

What brand plugs and coils were installed ? Did you apply dielectric grease to the boot ends to seal out moisture? Have you check fuel injector on #3 ? A flashing CEL is telling you have a mis-fire condition obviously from the P0303 DTC. I would change the fuel filter like Montana stated and check the condition of your fuel pump driver module (FPDM).

 

Try cleaning the MAF. Def could be a player in that your speed and conditions elicit a need for higher air volume's and a MAF issue could then come into play that doesn't in other situations.

IDK, just a thought and easy to check.

 

I had a vibration that i couldn't figure out where it was coming from, i checked the coils plugs wheels, and one day i decided to climb under the truck thinking it was my exhaust and just happened to grab the drive shaft to pull myself and i felt a clunk. The four bolts holding it to the rear pinion moved and it wasn't just a little loose it was a few threads holding on.