I know, it seems like alot of 5.4 topics on here. I have a 1999 F150 with the 5.4. I have 160,000 miles on it, and about 80,000 of those are pulling a trailer. I have a loud tap/knock coming from the driver side of the engine at all times, but it gets louder and faster under load/acceleration. I would guess that it is a lifter tapping, but I don't even know if these modular motors even have lifters. LOL! Anybody have any experience with this? Any idea how hard it would be to fix?

1999.160k miles,pulling a trailer.that is a rod knocking.if you want to save the block,you better get it to a motor exchange place.

Could it be detonation? Just my guess. How long has it been making that noise? I believe they have hydraulic lifters, unless it's a SOHC motor.

I have a 2000 f-150, 5.4L with 230k miles, tow a boat a few times a week and it recently broke a couple of exhaust studs at the exhaust manifold which causes some tapping type noise. May want to check it out unless u can for sure tell it's coming from a tappet or rod which I doubt unless the oil ran low or wasn't changed in a timely manner....

I have a 1998 f150 and the same sound comes from my truck ( or at least it fits the description), it only happens when i accelerate. I had the ford house look at it and they could not find anything that was wrong with it.

About a year ago i had a louder tapping sound, it was something about the catalatic converter was loose... a simple weld fixed that prob. though

Now my check engine light never goes off... the o2 sen. are out.. i change them same thing happens... changed all the spark plugs cause they said it was running to rich... ell if i know i just drive it...

No lifters on the 5.4. They do have a history of premature wear on the rocker arms. I do not know if that would make the noise you are talking about. I would get a listening device and try to determine where it is coming from. If it is down low in the block you had better start looking for a rebuilder.

They have what it's called: HYDRAULIC LASH ADJUSTERS

Thanks for the responses. I checked with Dallas Mustang, and they said I would be looking at round $3,000 for a rebuild. I think I will just drive it till it blows up and then get something else. Now my check engine light came on saying bank 1 and 2 were running lean. I am going to pull of my MAF sensor and clean it, clean the throttle body, and replace the fuel filter, I hope that will fix the light. Lol.

Steve call me.

Well Stan, I looked into that stuff we talked about, and I guess I was a little late. I blew my motor Saturday. I am thinking about going with a crate motor, does anybody know of any good crate motor builders?

Steve
call Jasper engine rebuilders.1-800-827-7450