I have an 06 5.4 Lariat. Changed the plugs this past weekend because it would start skipping around the 40 mph mark. Used motorcraft sp515's. Anyways, truck ran fine for two days then tonight when I was leaving work, it cranked up fine started shaking a bit then cut off. Cranked it up again, same thing. Now when I crank it up I have to rev it up high for it to stay cranked and sometimes it wont even stay cranked long enough to rev it up. Any ideas what might be wrong. It ran perfect for several days and now this? Thanks

 

Check the plug ins on the cops. May not have one plugged in good and it worked loose.

That's where I would start, good luck.

 

thanks for the reply, ill do that before I send it to the dealership

 

Any DTC's?

 

It's still where I work, it won't stay cranked so I'm probably gonna have to have it towed, it worked fine all day and now won't stay cranked, the battery and transmission light comes on, then oil pressure drops

 

Well did some research and thought it could have been the fuel pump driver module after some post on here. It was pretty corroded so I replaced it. Still doing the same. So I just had it towed to the mechanic because that is the extent on my car knowledge. Hopefully he wont rip me a new one.

 

ended up being the mass flow air sensor

 

Glad you found the problem and thanks for letting us know what it was.

 

No problem, appreciate the help