The 5.4L is an overhead cam engine. That means instead of a single camshaft in the center of the engine, close to the driveshaft, the camshafts (two in this engine) are at the top of the cylinders. This requires longer timing chains. The longer a chain is, the more susceptible it is to stretch. Each link of a chain might wear a tiny bit, but the more links in a chain, the greater the total wear.
Then there’s the issue of timing chain tensioners. You know how a bicycle chain has a little slop in it unless there’s a spring loaded gizmo taking up the slack? A cam chain tensioner does the same thing. The ones in the 5.4L engine wear out faster than normal because of the material they’re made of. If there’s too much wear in the tensioners the chain might jump a tooth, throwing timing way off and damaging the engine.
(Chain stretch is why many overhead cam engines use toothed belts instead. They don’t stretch, but they eventually rot and break. Pick your poison.)
The second generation 5.4L, produced from 2004 to 2014, has three valves per cylinder. This one has several problems, some of which are related to inadequate oiling.
Upon tearing apart failing engines, mechanics discovered the buildup of sludge and debris clogging the oil passages, particularly in the cylinder heads. Some say the passages are too small. Ford released TSB #07-21-2 recommending that affected engines be cleaned and flushed to remove any debris from the oil passages. In some cases, engines needed to be replaced. Mechanics advised changing oil and filters much more often than recommended in the owner’s manual.
The 5.4L 3-valve engine features Variable Valve Timing (VVT) that can slightly adjust the camshafts on the fly for either greater fuel economy or more power. The camshafts are adjusted with cam phasers. The cam phasers are controlled by oil pressure. See oil pressure problem above. Also see TSB #06-19-8.
On top of this, owners have complained of excessive oil consumption.
The second generation 5.4L also has the timing chain stretch problem.
Conclusions
Some mechanics, such as YouTuber “Car Wizard” who waves a long list of replaced motors, say to never ever EVER buy anything with the 5.4L engine. But to be fair, the mechanics see only a portion of the millions of Fords with these engines. The rest will faithfully serve their owners. If that weren’t true, outraged customers would’ve killed off the engine — and maybe Ford — long ago. The problem is we don’t know which engines will go bad, or when. To repeat what I said at the beginning, I’m writing this so you can make informed decisions, know what to be alert for, and take preventive measures. Also, I’m sharing this so you can see the importance of having enough in your emergency fund to cover a possible engine replacement we hope never happens.
