You may have an O2 sensor issue?

 

I changed the plugs to Motorcraft first thing this morning. I put o2 censors on both banks just before the converter.

 

I don't think that the old ones were bad. I was thinking about changing them back just to see if there is a difference.

 

I'm getting just over 30 psi on the fuel pressure test.

 

Did a compression test #1 and 6 cylinders have 0 compression.

 

So it's running on only 2 cylinders.

How many miles are on the truck/engine? Are you the only owner?

Lastly... I hope you didn't just purchase this truck?

 

No, it's running on 6 cylinders.

You have valve, piston, or cylinder issues. Pull the valve covers and turn the engine over and watch what's going on. Pull those 2 plugs and take a look with a borescope.

 

The truck has in the neighborhood of 220,000 miles on it. I've decided to either do a complete rebuild on it or replace it with a crate ingine.

 

https://www.powertrainproducts.net/F...red-p/1597.htm

 

Oops, I misread it. The way it was written, I didn't catch it. Thanks glc.

 

[I had the same situation a couple of years ago on my 1998 F150. I have tried everything you have done even a home made smoke test. Did a lot of research on this website and I found a tread that helped me fix my problem. Funny thing was that the tread that I found was not on a F150, but a Ford car.
The problem was the intake manifold. Had to take it off and clean out all the valve ports and replace the intake manifold gasket. Now she running very smooth and more powerful than before.
Wish I could find that tread cause this guy talks you through it step by step with very clear pictures. Hope this info helps you.


QUOTE=Rond7485;5266643]2002 ford f150 4.6L Codes 174, 171 and 353. I have not found any vacuume leaks, the maf is good cleaned injectors changed pluga coils are good. I get a s.t.f.t. reading of -9,7% on both banks and 29% on both banks for the l.t.f.t. I can't figure this out. Full pressure is good. I don't know where to go from here. I thought a burnt valve but no smoke at all from the exhaust. The truck runs very rough. Any advice[/QUOTE]

 

Not going to help, he has 2 cylinders with zero compression. See post #20.