craigt502

Just bought this truck today.
5.4L 177,000 miles.
This does not happen all the time---- When the trucks idling the rpms will randomly dip down to 500 and the engine will run rough. I will give it some gas and bring the rpms up, and sometimes RPMs will stay normal 750ish and other times it will just dip back down to 500 rpms.

Any ideas?

jjubrey

Could be Plugs, COP's, Fuel Filter, Injectors, or possibly VCT's, Phasers, or a Vacuum Leak. Have you tried connecting a code reader to see if it will throw any codes? You could have some stored without a light.

vince_nt56

I know I’m late this, I have a 05 5.4 f150 doing the same, did y'all ever find out what was causing this?

Johnny Paycheck

Do you like the truck a whole bunch? If it’s never been done, you might need a timing job.

I would direct you to the 04-08 forum to see if this is something you want to take on in regards to cost.

vince_nt56

I have done a timing job on the truck recently, we made sure the phasers lined up with the marks on chains and the balancer at the bottom
New: chains, guides, phasers, and vvt solenoids
Tune up with oem plugs and coils

vince_nt56

could it be dirty Throttle body that I've been seeing?