The Drivetrain
A loud knock is usually associated with a rod bearing. The rod connects the crankshaft to the piston. If a rod bearing went out, possibly from an oil pump going bad, it would stall out the motor.
Loud things starting with K: klaxon
light slapping knock is a piston knock a loud heavy repetitive knock is a connecting rod Very Bad
My guess would be that motor is locked.
if its a loud knock from the bottom end, DO NOT run the engine, it is likely a spun bearing; have a professional look at it
Possible exhaust leak
The knock on the door was very loud
It is POSSIBLE, but highly unlikely unless you had prior problems with the timing. I would have it checked out by a mechanic as it could be any number of things.
The knock sensor is exactly what it says. It senses any knock or ticking in the engine and retards the timing. The knock sensor is not the problem, the knocking is. Go to a repair shop and have it diagnosed.
runnig hot and\or foaming.
Driving at 50mph or above what causes a loud knocking clicking sound during acceleration?
Check your transmission mount, it probably needs replacing. Check out www.thirdgen.org