3.8L. Oil Pressure

Just had the timing cover gasket replaced. Oil pressure drops when car is idling in gear and warm. When I put in park, pressure climbs to normal. There is no fluctuation in pressure when cold. Possible mechanic error when replacing timing cover gasket? Heads and headgaskets were also done due to overheating. Any suggestions?

Change the oil to a good quality brand in the correct weight for your engine and install a Motorcraft oil filter. Unless pieces of the gaskets got into the pan and are partially blocking the oil pump screen then what you had done shouldn't have affected the oil pressure. When it's idling in gear the rpm's are lower then when it is in park which would make the pressure drop a little. You could have done some damage to the bearings when the car overheated. This could have opened up the clearances and thereby lowering the oil pressure.