i have a 96 blazer 4x4 4.3l v6. ive been having some trouble with the engine idle sputtering and bogging down. i replaced the throttle position sensor, cleaned egr and egr ports, cleaned the idle air control valve(which i replaced a while back), and cleaned the throttle body as it was a little dirty. i also cleaned maf sensor just to be sure. now it idles fine but now i have a loud knocking coming from oil pan at least thats where it sounds like where it is coming from. running at idle in park without giving it gas oil pressure is below 20 and knocks a little, when driving as gas is applied between gears it knocks loudly. at a stop light while in drive foot on brake the engine oil pressure drops below 20 then cuts out and dies. ive done the lower intake gasket because of a coolant leak. i repaired it a year ago or so and caught and fixed pretty quick. since the intake repair ive never heard a loud ticking or knocking, but now that i finally fixed the rough sputtering idle, now i have this problem. the blazer has about 218,000 miles on it. i just recently changed the oil a week ago or so using an ac delco filter and using mobil conventional 5w30. i have been using 10w30 but i dont think that would have this kind of effect on it. i really dont have the time to drop the oil pan. i'm pretty sure its the oil pump. could i try draining the oil a little add a quart of trans fluid let it run for 20 minutes hopefully cleaning pick up screen on oil pump? im really at whits end with this truck ive invested quite a bit of time and money into this thing. any advise or confirmation would be greatly accepted.