Hello all! I just picked up an 08 Liberty 3.7 auto 4x4 with 80k and noticed it has a faint deep knock after it's warmed up. The knock is only there when in gear at idle. You can feather the gas and hear it but it's gone upon acceleration. I'm assuming it has a bad rod bearing, I'm just wondering if there might be something else commonly mistaken for a bad engine on these specific models. Any input would be greatly appreciated!!!!