I bought a 1999 F-350 6.8l V10 , anyway it only had 112k documented miles on it (bought it last year 2020), thinking that's nothing for milage on a domestic truck. So shortly there after it needed coils, I also noticed it tends to use oil about 1qt to 1500 miles, and if I can get it to get 10mpg I throw a party, it's usual is 8 or 9 daily highway. It's now started leaking oil in a few places, and the power has never been what I would have thought. Anyway, it now has 141k and it started misfiring again, so I threw a set of plugs and coils on it, still misses#8. Take compression, 45psi. It's only got 141k on it. Did I make the biggest mistake buying a V10? Pulling the motor looks like it's gonna be a "wonderful" time. And if I don't fix it it's worthless here in California. Please tell me that there is a simple fix like on the chevys where a little liguid comet in the cylinder scuffs it enough to clean the cylinder and then pulling up on the valves and spinning can clean em up a bit. Because I am so let down by this truck. I remember when Ford was Ford tough. I mean why a overhead came engine in a truck? Tell me something positive, even if you have to lie.

 

I too bought a 2001 V10 just last year. It is my first Ford vehicle I've ever owned. However, after doing much research I have discovered that the V10 and V8 Triton motors are generally very good even into higher mileage. Reading here you'll find a lot of guys over 200k without problems. My favorite thing about it so far is how easy it is to work on compared to all my Toyotas, and even compared to a Chevy S10 I had a while back. If you look at the Triton tear down pictures, the motors are very simple.

Anyway, as far as your misfire. Have you tried moving the #8 COP to a different plug to see if the misfire code changes? What type of COP's did you purchase the first go-around? You will want to buy the Motorcraft or Denso (or another quality manufacturer). I wouldn't trust the cheaper Amazon/Rockauto ones. Same goes with the plugs, stick to Motorcraft.

Where are the leaks coming from?

As far as V10 power... Try cleaning the MAF and Throttle Body. Replace your in-line fuel filter. 141k for these motors is nothing. Don't loose hope!!!

 

If you only have 45psi on number 8 it has a internal problem. A quick way to tell if it's valves or rings is do a simple blow by check by getting it warm and have someone power brake it with the oil fill cap off and see it oil vapor comes out. If it comes out it's rings but if it doesn't it may just be a valve problem
and a new head will solve it.

Denny

 

Did not notice that he was only getting 45 psi on cylinder. Woops.

Pour a tablespoon of oil in the cylinder. See if the pressure goes up, which would point to rings.

 

So a few questions occur to me here.......

-What does this "it needed coils" mean? One, two or all 10? What symptom or DTC prompted the idea any or all COP's required replacing? Were the spark boots checked for a possible misfire situation? Have they since been checked/replaced as needed?

I myself don't see too many downsides to overhead cam engines----they're far more simple than the traditional overhead valve engines which have their own set of operating issues. There are far fewer moving parts and that design lends itself to using the lighter aluminum heads. OHC engines don't suffer the "torture" of push rods, rockers arms and the attendant rapid change of direction/momentum the OHV engines contend with.

Your truck with that engine seems to have the typical oil "loss" the Modular Motors all have, its partially due the lower oil viscosity we're using today. In fact most here report a one quart oil loss about every one thousand miles so I'm thinking you're doing slightly better in that regard.

I'm running two 5.4's from 2000 and 2003 each with well over 285K miles--for the most part they've been reliable, easy to repair when needed but I keep on top of my maintenance---do you know for a fact what maintenance the previous owner performed----or ignored?

I've been driving different brands of vehicles for about 54 years---don't give me the eye roll just yet --and there's not been a one that did NOT have its design "flaws", things I thought surely could have been done more to my liking. For my purposes the Ford brand delivers all I need and expect and despite being an almost life-long GM performance fan I'd not trade my 5.4 E-Series for much of anything out there today.

Just my $0.02 worth mind you!

 

If the engine does need to be removed, I will say its not a horrible job. About 3-4 hours if you know how to turn a wrench.