Tapping at idle when warm

[moparxx1]

I have 01 Sport Trac 4.0 SOHC....After starting and allowing the engine to warm and after idle settles to its lowest point I get a tapping noise from engine and if I raise the idle just a little the tap goes away... Just looking for info...THANKS....Do not hear while driving or when still cold....only after engine warms....and goes away with increased rpms

 

[MidnightRebel07]

Does it sound like a tap or more of a tick.tick.tick...? Just an idea but take a spray bottle with salt water or window cleaner and spray it on the spark plug wires close to the spark plugswhile the truck is running, you'll see electric arcing coming from the wire and going to the head.