I was driving about 45 mph yesterday and all of the sudden the truck started misfiring and shaking really bad. The engine light was also blinking. I limped home about 6 miles away. After a couple of hours I drove it 2 miles away to O'Reilly Auto Parts to have the codes read. It was still misfiring and shaking. I was told there was only 1 code (misfire cylinder 5). I replaced the coil pack on cylinder 5. No change. I drove the truck back home. With the hood open I heard something that sounded like a click (something related to a vacuum release) about 5 to 10 seconds after I turned the truck off. I don't recall hearing this noise before. This morning I had it towed to a Ford dealer. They only had one mechanic working today and didn't get to do much to it. They did call and tell me he did not think it was plug, coil pack or fuel injector. He said the mechanic thinks he hears something internal to the engine that doesn't sound right. They plan to do a compression test on Monday. I bought the truck new. It has 116000 miles and has always had oil changes at the Ford dealership. I replaced the plugs at 95000 with original Motorcraft plugs. I'm hoping this is not something that requires a new engine. What are the possibilities and associated costs?

 

Maybe valve train related?

 

Dealer called and said no compression in cylinder 5. Next step is to take valve cover off. Not sounding good. Any specific questions I should be asking? Any opinions/advise?

 

Worst possible news. Rocker arm broke, dropped rod... New Engine needed. 8600.00 with a 3 year unlimited warranty.

 

Could they tell you what caused it to break? or was it just a fluke thing?
I have a 2006 5.4 with 200k mi and I definitely want to keep it running as long as possible

 

It was actually an exhaust valve that dropped into cylinder 5. They said they had never seen that happen with that number of miles with such an excellent maintenance history. I ended up trading the truck.