Before you say bearings, rod or main, check it out. So the vehicle wind sheild started leaking which is a common problem on these so the person let it sit for a couple months. It got moisture inside, caused mold and presumably the reason why things are a little rusty where the interior metal is exposed. I changed the battery and the alternator, and i am still getting the same battery light intermittently. Also my radio, clock and something else doesnt work either. Aside from those issues i am having, i thought it was having an issue with timing, because i get a fairly quiet, hollow, knocking, that sounds more like something shaking back and forth, or a thicker piece of sheet metal flexing and making popping noises. NOWWWW it gets weird. I have adjusted all but the ac belt, but it hasnt stopped the battery light or knocking/misfire/whatever. Buuuuut..... If i turn on the air conditioning, the knocking stops for 98 % of the time i stand there and listen, and i put a screwdriver on the bottom to listen and heard very infrequent tapping only sometimes. Whut the stuff?

my ideas are as follows in order of most likely to me.
ac compressor adds pressure, allowing an off center crank to be pulled back to center, a rod bearing that may be loose, a problem with the computer, or(pure shot in the dark)!! The ac was on constantly, and i assume on when the vehicle could have been over revved, and strained, and this could have caused damage on a bearing or multiples, and now when i dont use the AC, The crank/bearings/rods WHATEVER it is, doesnt sit at "home" unless it pulled back to "home" by the compressor. Idk guyses. Any idea?

 

AC doesn’t move the crank around. What it does do is place more load on the engine, so the ecu adjusts the fuel and air to keep the rpm steady, and that bit of extra load means that the rods aren’t clunking as much. If you have your ac off and it’s in gear, does it knock? If you apply a little bit of throttle with it in gear, does the knocking go away? Sounds more like worn wrist pins if that’s the case. Or piston slap, pretty common.

 

The only consistently effective stimulus is the AC compressor.
Revving it doesn't directly affect it, most times it gets louder, it can get quieter though. Finagling the TPS can also get it to almost stop, but its not a long lasting solution.
When i said the AC stops the knock, i mean if i turn the AC on, and i slide under the car and i put a screwdriver to the pan and my ear and the knock is VAMOOSE. Gone gone. Like 98%. Not quieter, but silenced. It sometimes makes a light tap every few minutes, but this is why i cant really figure anything else except the ac puts the crank back the "fleas hair" of a distance that it is off kilter. Does it make sense, that if the ac was on and applying new torsion, and someone punched the gas and the crank was jerked too much, couldnt it have rubbed certain spots in the bearing and caused a variation thats only noticable when the vehicle is no longer at original point of damage specs? (Not having The torque of the AC like in hypothetical engine damage situation)
Correct me if i am wrong but if the ac pulley isnt necessary, and its truly and actually stopping the knock, doesnt that mean crank is moving the pulley over? I thought in order for torsion to occur, it required some sort of change in motion to the object being torqued (im talking 100ths not inches). I know it doesn't drive the crank, if thats what you were saying

 

UPDATE!!! i tightened the ac compressor, and it stopped.... The knocking in the exhaust is louder though? Long term Fuel trim is lean bank 1 so i figure its related.