I've had an annoying issue that has popped up over the last couple months. When my engine is cold (worse on cold mornings) the engine knocks pretty bad. Idle is fine and it only does it after the initial idle up and clutch fan stops right after start up. It knocks until it I drive it about a mile and the engine warms up. Once it stops the engine purrs like its brand new. There are no drivability issues and MPG has not changed at all. It is quieter on warmer mornings and doesn't last as long. I run 5w-20 Mobil 1 and use a motorcraft filter. Engine is a 06 5.4L with 88k on the clock.

It seems to me like something isn't getting sufficent oil until it gets driven a little. I was worried it was the the Cam phasers but it runs good and quiet when the engine is warm so I don't believe thats what it is.

Any ideas?

 

Sounds like to me you have a manifold leak. It will be loud on cold start up until the manifold warns up and closes the gap. What happens is usually a stud breaks that holds the manifold to the block and allows a gap to form. There is lots of info on this problem on the forum

 

I had thought about that, and it makes sense. I'll check on it thanks!