I re-read your post several times. I'm not saying that lifters stick to the cam; obviously this can't happen if the engine is turning.

My point is that hydraulic lifters themselves are compressible, with metal sliding against metal. Inside of this cylindrical assembly is a spring, as well as an oil passage. This compressibility helps the valve train to absorb some of the mechanical shock and allows longer life; this is the advantage of hydraulic lifters. When lifters get "sticky" the two pieces of the lifter (that normally slide freely) exhibit increased friction, whether due to metal-on-metal wear or sludge or dirt deposits or something else. After the lifter is compressed by the cam lobe, a sticky lifter will maintain its compressed size rather than rebounding to its "full" length. This creates a slack in the system, resulting in a very characteristic "ticking" sound.

A semi-related problem is when high revving engines create too much oil pressure and a lifter "pumps up", preventing the valve from fully closing even when the lifter is on the base-circle of the cam lobe.

If you tell me that my 2.5L I-4 doesn't have hydraulic lifters, then I will believe that the "ticking" that I've been experiencing is not due to a sticky lifter. However, after you questioned me I was forced to query my Haynes manual (ugh, wish I had a Jeep FSM) to ensure that this is in fact a hydraulic lifter, OHV engine -- which it is. If you have your Haynes manual for Wranglers 1987 - 2000 (which is in my lap right now) please see section 2A-9, paragraph 2.

If I missed something or you don't understand the point I'm making, please respond, but please reply with more than "reread my post".

Thank you.