I have a 2001 six cylinder F150 with 90.000 miles. When starting in the morning, everything is normal until I get 100 yards down the road, when every lifter starts to clatter. This continues until the engine has warmed up completely. At idle, the engine sounds normal, only when under load will the clatter get loud. Oil pressure is good, fuel pressure is good. After a trip on the road, very little noise.

Help, this is a good truck, need to know what to fix.

 

Not sure if it snows in the winter where you live but if not try changing to a 50 weight oil.

 

Using 50 weight oil is a very bad idea in the 4.2L V6.You'll blow seals everywhere.
The noise you are hearing is probably not the lifters but the butterfly valves in the intake manifold. They rattle like a loose door in the wind. There are small plastic bushings in a housing at the back of the motor squeezed in by the firewall that hold the shafts to these butterflies. When they break you get the noise.
They control the fuel air mixture at startup then open fully when the motor is warm. They are a bi#$#h to get at for repair. I removed my upper intake manifold to fix mine. Good luck BTW it won't hurt to run it like that.

 

Bad oil filter. Use motor craft and max 10w30