Recently my seldom-driven 2005 F150 5.4 (48,000 miles) went into idle-only mode. Fault code said throttle body was stuck, but after sitting for about an hour, it ran fine. I replaced the throttle body anyway and put a new throttle position sensor on the old body for a spare. I'm contemplating taking the truck on a long trip next year. How common is this failure on the 5.4 V8?

Is there a simple wiring change to the light switch that will permit the stock fog lights to remain on with the high beams?

Many thanks!

Jim

 

Thanks for the reply. The truck is driven about once a month, admittedly mostly short trips of 10 miles or less, and it's stored in near ideal conditions -- in my drive-in basement where it is dry and the temperature ranges from 60 to 80 degrees. Yes, despite its low miles, it is 15 years old, so I guess there are consequences due to its age. It's encouraging to know that my throttle body problem is not too common.

Thanks again.

 

Mine has a bit of an interesting history. The paint shines nicely, even on the horizontal surfaces but with some nicks and dings here and there, and the plastic headlights are as clear as new. I bought it from a retired Army sergeant at about 45,000 miles, and I asked him where the truck had been all its life. Seems the truck spent much of its life in Korea. He was able to take his family and a vehicle there. They lived in an apartment building with under-building parking, so the truck saw little sun. He walked to his nearby office job, and the truck was used only on weekends. He said the nicks and dings were mostly from shipping.
The truck had (has) new tires, and the antifreeze had been changed shortly before I bought it. He wasn't a DIYer, said he relied on the dealer for maintenance -- don't know what he did for maintenance in Korea, except that he said he had the plugs changed there at 31,000 miles (leaded gas maybe?), so I don't know what plugs are in the engine. I changed the oil and brake fluid just after buying the truck and added a can of R134 which it probably didn't really need. Except for the recent throttle body issue, everything has been fine.

 

I have a 2005 Expedition 5.4 with 179,000 miles. Just replaced the throttle body and the mass air flow sensor. Was out of town and it died; was towed to a dealer. They are claiming that the MAF harness is bad and they require 4 hours labor. I know it is just a connector up top on the MAF. Is there not a connector down below and why would it require 4 hours labor to change. I have not been able to find much on the harness replacement; any assistance would be appreciated.

 

I haven't run into that problem, so I had to take a look at my Haynes manual. Changing the MAF looks like a 10-minute job, but the wiring harness is a different issue. There's no telling where it goes, and it's likely part of a larger multipurpose harness that serves several electrical components. The typical consumer shop manuals seldom provide that much detail.

 

Thanks. I am by no means a mechanic, but just an old fart that likes to tinker and do things myself. I have access to Chilton's online DIY version, but can find little on the harness. I guess I will find out when I get the vehicle back and can look at the configuration at the bottom end of the harness. Just seems an inordinate amount of time to change the wiring harness.

This is my second expedition; I had a 98 with 380,000 miles on it when I retired that one.

 

Continuing this theme, I have just returned home from the trip I mentioned in post #1 of this thread. I was towing a trailer, total weight about 4,000 pounds, that the truck handles easily, on a round trip of about 700 miles each way. Almost immediately after departure, the CEL came on and the truck began to misfire badly on long hills. OBD checks at different times have shown misfires on cylinders 2, 4 and 8. At the destination, a mechanic swapped coils around, observed a change in the engine running, and declared the problem to be coils. So I authorized the replacement of all eight coils with OEMs. However, that didn't fully eliminate the issue, a misfire still occurring on cylinder #8. The #8 spark plug was pulled and found to be essentially destroyed with the electrode missing and bits of the skirt below the threads broken away. The plug was replaced and all seemed well, with the truck handling the return trip perfectly, no CEL -- for about 100 miles when the misfires returned along with the CEL. What I am having difficulty understanding is: The previous owner said that the plugs had been replaced at only 31,000 miles, and now the truck has 50,000 miles and apparently needs plugs again, only 19,000 miles later. What is causing this engine, a 5.4 Triton, to eat plugs?