Not good ......
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Your story is (unfortunately) familiar ........ I have read a few other posts similar to this - on this site and a few others ....
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There is a good chance there is some 'damage' to a rod and/or crank bearing. An oil pressure gauge would help in this case ....
a scored bearing will usually result in low oil pressure readings.
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How long ago - miles - was the oil changed before the knocking occurred ...... ?
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