thanks for replys guys. I changed oil (0w40)and filter and new oil pressure sensor. filter looked defformed and full with little particles like metal and plastic. i bought this car because it had broken timing chain guides and broked distributor cap. chain skiped 2 teeth on intake camshaft sproket. i installed new upper and inner side guides, reset timing. didnt checked compression yet but engine sounds very healthy(no bent valves) ecxept knocking in mornings. so after oil change, thank god, oil pressure is up to 2 on hot idle and goes to 3 when engine at 3k rpm. can i change that sticking valve myself? also how hard it is to remove oil pan? i heard you have to lift the engine or something?
thank you for help
victor

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1999 ML430 Silver 135k ml
Smoked LED taillights, Alpine in-dash DVD player, 12" sub, Pioneer components, 2 amps, 4200k HIDs, ML55 headlights, 20" rims, mirror LED blinkers

SOLD. 1996 E320 145k ml. Burgundy

SOLD but miss it everyday 1992 500sel Black
Chime buzzer mod,Alpine CD/MP3 player with stock amp,Euro headlights,S600 grill,20" rims, BEST CAR EVER!

SOLD. 1990 300E White
187k ml,smoked tails,Euro headlights,17rims,Intake,12" sub in first aid kit,alarm/autostart,buzzer mod