I have a 2000 Jeep Wrangler with roughly 160K miles. Recently I let it sit for a week and after sitting, I cranked it & it had developed a "tick noise" which sounds like it's coming from the top of motor or the front of the motor. I changed the oil & added 1 quart of resin to it, but the "tick" was still there. I was told to change oil again & add Marvel Mystery Oil, crank it & let water temp raise, then drive for 30 min's. I did this & the tick has very slightly gone away but still remains. I removed oil cap & noise never got louder, I was told to do this & maybe it would be a lifter. Oil pressure stays at 40. The noise does get louder at high rpm's.
I've been told its not a exhaust leak, I have noticed a loss in power (I think, haven't been in Jeep for 3 weeks) so it seems slow. I was told it couldn't be a loose rocker arm also.
The noise can sound like its coming from under the timing cover too. Could there be anything in there slapping against anything?
Im open to any & all suggestions. Im gonna pull valve cover off this upcoming weekend, but wanted all opinions before before hand, maybe some have seen or heard of this. THANKS in advice.