I need some suggestions on what the culprit may be. (Or culprits)
Truck: 2004 Lariat, 5.4L 3V, only 114k miles. No after market mods or even major work done on the truck. Pretty much all stock. I keep it regularly serviced. New plugs in at 100K. Clean the mass airflow sensor and throttle body once in a while, and replace air & fuel filters.
Issue: Continued loss of power and fuel efficiency. Now at 10 miles per gallon. No codes or warning lights ever showing. This truck use to regularly pull camper trailer fine. Last week I pulled a trailer - it struggled big time. It now constantly feels sluggish, like the e-brake is always on. (It's not!)
This is a really good truck in good shape (otherwise) and I want to keep it going for a long time. Before I just start guessing and throwing money at it - I'm looking for most likely contributors to power loss that don't show codes. Fuel injectors? Ignition coils? Wiper fluid?
Oh yeah, I did change out the O2 sensors this winter as a quick guess at lowish cost. No effect.
Thanks for any input. - Corey

 

Get it checked for clogged cats.

 

You would probably have noticed if the brakes were dragging but check the rotor temperatures after driving it to make sure. glc probably guessed correctly.

 

Also make sure nothing is blocking the air intake.

 

Rev it up quickly in neutral and see if it bogs at high rpm.

 

Roadie - Tried that - it was smooth revving up and down. No bogs or stalls. Thanks.

 

glc - A quick look didn't find any blockage. I'll search some more this weekend. Thanks.

 

Question: Will things like fuel injectors and ignition coils "go bad" without creating warning codes? What similar parts might reduce power as I've described above, without being so bad to create codes? - Thanks

 

If injectors or coils go bad it would probably run rough. Take it to a muffler shop, they have the equipment to test for cat and exhaust blockage and restrictions.

 

IMHO....blocked cats or the ecm is failing

 

Many thanks glc and beechkid.

 

It's a 3 valve. Welcome to the world of variable valve timing gone wrong. I'd say there's the possibility you have lost the extra oil pressure/volume necessary to advance the cam timing. The cam phasers on those trucks are actuated by oil pressure. The 3 valves are NOTORIOUS for cam phaser failure and low oil pressure in the heads; I'm sure you already know this. My first course of action would be to put it on an active scanner and drive it with the scanner attached. Let the mechanic read the valve timing advance from the passenger seat while you drive; he should be able to see if they are actuating fully and within an acceptable time frame. It may not have actual error codes for the cam phasers (yet) because the computer always allows a delay with that system for the time between the throttle is mashed and the time the oil gets there, and so long as the phasers move within a pre-programmed amount of time and to a predetermined range, it won't set a code, irrespective of whether it's right or not. If they are not actuating fully or the valve timing is otherwise out of spec, the engine can still run, just low on power (like you have).

If putting a bottle of STP in it brings your power level back to normal, prepare yourself to do a timing chain/oil pump/cam-phaser job. Make sure whoever does it puts in GENUINE FORD 3rd design Cam Phasers and a MELLING 360-HV Oil Pump and first design cast iron/steel chain tensioners against your steel backed-nylon chain guides. If you want more info, just find Brian of FordTechMakuLoco on YouTube. He has all of the info you will ever want to know about the Ford 3-Valve.

Hope this helps.
Regards.

 

Great info ThrillsMan79 - thank you. I've seen some of FordTechMakuLoco's channel - great stuff. I do know the 3v is problem prone in this area. Just a big pain when it's sneaky like this. Cheers!