Looking at a 2004 F-250 with the 5.4 motor. Has 150,000 on it.
I have heard of some problems with the heads and spark plugs with this motor. Anyone have experience with them ?

The 04 model in the 250/350s is probably the best of them. They had the PI heads that made 20 more HP than the original design and weren’t as bad about spitting spark plugs. They did not have the 3V heads the 1/2 tons got that year that were bad about sticking plugs and breaking them off when trying to change a set.

Plug spitting issues can be cured permanently on 2V heads with TimeSert inserts. They take special tooling to install but are a good fix and a one time deal.

Timing chains may be getting tired by now, they’re tensioned by oil pressure and have plastic guides that may break. There’s kits to fix issues with them as well.

Or you may get one that will run forever and need nothing. I ran a couple up to nearly 200k with minimal issues and my uncle had a 97 he bought new that he ran to over 300k with no trouble. Local guy had a 99 he put 400k on with minimal issues. Never know.

That's the Intel I'm looking for !!!

My 06 with the 5.4 has over 330k on it with very minimal repairs. Still runs good. I do have a spare engine for it, actually I bought a part of a truck ( guy was making a pretty runner) so I got everything from the transfer case forward as a spare.

You never know, I'm pushing that 5.4 with 330k on it.

This is great to know. I have the little brother of the 5.4, the 4.6 in my F-150. I’ve got almost 240,000 trouble free miles on it. I hope it lasts for many more years. I like the truck enough that I would rebuild the engine to keep it going.

Keep the fluids changed frequently.
Used to be true, true today, always will be true
that fluids are cheaper than parts and labor to
rebuild something

I've got an 06 with 230k on the clock. Still runs great and doesn't use oil. It DOES burn gasoline though.

I've got a 98' 5.4 with 190K, runs great . It will use a little oil when ran at highway speeds. Less than a quart in 700-800 miles.
I had a friend in Florida who has 450K , the differential went out, he said the owners manual said it was good for the life of the vehicle. I told him the life of the vehicle is considered 100K, he said- Oh.
Another friend had 325K on a 97 4.6ltr.- bought it used a super abused it- no oil change or filter- add oil when it's low. It dragged a car hauler trailer 5-6 days a week loaded with about 2500lbs. His 25 year old son totaled it- towing an old limosine .

I've heard/read the 11th Gen. trucks with the 3 valve variable timing could be troublesome. Less so if you keep good fresh oil in them. 2004-2008 . There was an overlap with the F-250/350 that I don't remember the details on.

Loved my f250 v10. Was a 2V 2000 model.

Ran it 200k some miles before I sold it. The mod motors are solid.

The best field engine mechanic I know ran only F350s with the 5.4 gas burner. He told me they are great engines but they are sensative to good maintenance because of the cam phasers and a few other valve train parts. If not maintained properly or the wrong motor oil is used those parts are ticking time bombs. I've owned 3 of them since about 2005 and all have been solid and 100% reliable.

I have a friend that bought a 1997 new with that engine. In 2020 at 400,000 miles he put a factory rebuild engine in it. He loved the truck and the original engine but said the new engine just didn't have the power of the old one. He sold his old truck and went to a 2020 F250 with the 6.2.

I have a 2010 F-150 with 120k miles, no issues to report. I also heard the stories about the plugs, I changed them out a 100k without any problems.

My 2005 has almost 300,000 miles on it. Changed plugs at 75,000 mile intervals and oil at 3,000. Other than the routine maintenance I have never had an engine issue. Motor don’t use any oil and no leaks.Did have to have trans replaced at 170,000. I still have the truck but it’s now my beater / plow truck at camp. Current truck is a 19 F150 with the 5.0 3:73 gears and average 20.3 mpg. Not to crazy about the transmission.

Same, 225k when I sold it to a friend and is still going strong in limited use. Had all the original plug threads, trans, AC pump, PS pump.