chetubi: After I posted I thought that you may misunderstand. Yes, all engine forums are about problems, that is their nature. But that wasn't my intent. In fact, it is my understanding from BajaSportsMobile's postings and others that the Ford 5.4L is a very reliable engine. I referenced the ford-trucks.com modular engine sub-forum so that you can learn about your engine and be proactive in any ways possible so as to avoid what problems, if any, others may have experienced. Knowledge is power and fore-knowledge is much cheaper than post-. I meant to help, not to scare you. There is nothing for you to be afraid of:
"5.4L
...
The engine is only currently used in the E-series, Expedition, Lincoln Navigator and a 550 hp version in the Shelby GT500.
...
The 2-valve SOHC 5.4 L engine was on the Ward's 10 Best Engines list for 1997–1998 and 2000–2002.
Vehicles equipped with the 16-valve SOHC 5.4 L include the following:
...
1997–2014 Ford E-Series, 2-valve SOHC, 255 hp (190 kW) and 323 lb·ft (438 N·m) ratings for 1999 and later model years"
See:
https://en.wikipedia.org/wiki/Ford_Modular_engine
If yours is a 2008 E-Series then it is the 2-valve per cylinder (i.e., has 16 valves for the entire 8 cylinder engine).
(The 3-valve 5.4L which apparently some people hate because it has variable timing was never offered in the E-Series.)
(My now sold 1993 Bronco and my current 1995 Bronco both have the 5.8L/351Windsor engine which was replaced after 1996 by the Modular engine. FYI, my 1993 Bronco was at 200,000 miles when I sold it and still running strong. My 1995 Bronco is at ~125,000 and is also running strong. Your engine benefits from an even newer design, so I think you are in very good shape.)
Linear Mode
