1st it locked up. Now loud tapping

Sounds like you have a torque converter bolt that has come loose and backed out to where it is catching on the engine block. Pull the sheet metal inspection cover off, then rotate the engine by hand and look at all four bolts. A potential clue to this problem is if you find a lot of metal filings in the area.

The reason you can feel a misfire is because when it occurs, the crankshaft rotational speed slows down for just an instant. That speed change is how the Engine Computer knows which cylinder is responsible.

To hear a noise means there's a mechanical problem. That doesn't have to cause a misfire, although the cause of the noise and the cause of the misfire could be related. A broken rocker arm would be a good example.

I think I'd search for the cause of the noise first. There's a chance fixing that will take care of the misfire. Fixing a misfire is not likely to fix a noise.

A cylinder leakage test will identify the reason for the low compression. Burned intake valve, burned exhaust valve, worn piston rings, and leaking head gasket are common. A small leak in the head gasket won't cause a huge drop in compression.

There's two causes for water in the oil. Condensation of humidity will cause a white cream-colored goo under the oil cap. That comes from a lot of short-trip driving and doesn't really hurt anything. It burns off on longer trips. A leaking head gasket can leak coolant into the oil drain passages or into a cylinder. In a cylinder it will be burned and go out the tail pipe as white smoke. In the oil, the level will go up and the coolant level in the reservoir will go down. Antifreeze in the engine oil can have very bad results. It dissolves the first layer of metal on the soft engine bearings. That leads to excessive clearances and knocking.

The definitive test is to add a small bottle of dye to the coolant. Later you search with a black light. The dye will show up as a bright yellow stain. If it shows up in the oil, it had to get there through a leaking head gasket or cracked head.

A cooling system pressure test can also be helpful. The engine might have to be at a certain temperature for the leak to occur. Look for a rising oil level or a cylinder filling with coolant.

DOC

DID YOU SEE HIS VIDEO?

IT REALLY SHOWS/ SOUNDS THE SEVERITY OF WHAT'S GOING ON

THE MEDIC

Yup. That doesn't sound like rod knock. To me it sounds like something hitting the torque converter inspection cover.