Was it parked because of tick? I'd venture a guess while it was sitting a while a lifter collapsed and clogged up. Best thing you can do is change the oil, seafoam or whatever treatment you like to use, and take it on a nice highway drive. No reason to pull the valve cover off yet.

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1985 500SL Euro w/ AMG bits 130k
1984 300SD Turbodiesel 192k
1980 240D Stick China 188k
2001 CLK55 AMG 101k
2007 S600 Biturbo 149k Overheated Project, IT'S ALIVE!!!