I have a 2014 f250 with 6.2 gas motor. After washing truck or when it rains, there is a tapping noise, almost sounds like a lifter. After you drive down the highway and it dries it completely goes away. Sometimes I feel a slight hesitation but nothing major. No engine light has ever came on.

 

Tapping or ticking? (I realize it's slitting hairs).

Typically ticking can be the injectors, the PCV valve or an exhaust manifold gasket leak.

Tapping is more deep in tone, and typical of something touching another component.

 

If it only happens when its wet then I would say it's not a internal engine problem but something getting wet. The very first thing I would look at is the air cleaner cover. Sometimes it can be hard to get seated and that can cause the hesitation.

Denny

 

sparkplug wire arcing while wet???