Hey guys, I have a 99 with the 5.4 and is making a tapping noise when running between 1600 and 2100 rpms. Any ideas ?

 

I would check for blow bye or worn ring(s).

 

I have a 2000 5.4l that does the same thing. It starts between 1600 and 1800 rpm and continues to 2200rpm. It doesn't start until the engine is warmed up and then continues. Ford dealership told me it was carbon build up. Two other mechanics told me either wobbling piston or lifter rod. Have you found out anything else.
The tapping got louder in July and over a larger range of RPMs. Back to the Ford dealership and told normal engine noise. Just over two week ago the engine threw a rod on the freeway while my son was driving it. Don't think Ford dealerships are staffed by competant machanics at all.

 

I checked the plugs and they are all tight. One guy on another site told me it could have something to do with the alternator, but I'm not real sure about that. But you're right, only does it when it warms up. As soon as I find something out, I'll be sure to let you know.