Welcome to 2CarPros.
A loud knocking from the engine is usually a crankshaft main bearing or a connecting rod bearing. Make sure the oil is clean and full. Then, read through this link. It discusses the most common causes of an engine noise.
https://www.2carpros.com/articles/engine-noises
Read through that link and see if anything mirrors what you are experiencing. Let me know if I can help in any way.
Take care,
Joe
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Wednesday, March 20th, 2019 AT 7:48 PM