I noticed a ticking noise at idle this morning and can feel a "tick" when I place my fingers on top of the coil 4 but not the others. I won't get a chance to pull that coil and plug until I get home today but had a few questions. Is this just a loose spark plug ? Valve noise ? anyone experience something like this ? I have 160K miles and I don't think the valves have ever been adjusted that I am aware of, purchased this used at 130K.