Knock and tick
 

Ok i have a 1990 mercury grand marquis LS 5.0 with aod and ive got a serious knock and tick, lower end knock high end tick. I know the tick is lifters but my knock only happens when im in park. And when the car warms up to fully operational temps my oil light comes on when i come to a stop and flutters with the rpms when i take off till i hit higher rpms then it shuts off. And in Addidtion to all that my car almost seems like its misfiring at low rpms and during take off. Its got very little to no power when im just cruising along and it shifts up. Thanks in advance.