Don't have a good answer for you until someone tells you what they found and you report back with that information. If the oil pressure warning light wasn't on, or the gauge wasn't bouncing up and down, my suspicion is it is not related to engine bearings. Also based on the low mileage I would hope it's not the bearings. If the mechanic says it IS engine bearings, ask to have an analysis done on the oil to see if there's some contaminant in it. If the engine is still under warranty, the dealer will have to work on it so don't spend any more money on a diagnosis at an independent shop.
There are other less-serious possibilities. The vibration damper can break apart or come loose. The drive belt pulling up on that can make a loud knock twice per revolution. If your engine uses a knock sensor as most do today, the Engine Computer will know there's a knocking taking place but it won't know why. It will retard ignition timing in an attempt to stop that from occurring. Severely retarded timing reduces engine power.
Some engines use a timing chain that slides over guides that help to keep it tight. Those can break and let the chain slap against the housing. If it jumps a tooth or more, that will retard valve timing and make the engine have very low power, poor response, and once you turn it off it is usually hard to restart. Most import engines are of the "interference" design, and a timing belt or chain that jumps more than two or three teeth can result in bent valves. That can turn into a pretty expensive repair. The best solution if that is a possibility is to stop the engine right away and don't try to restart it. If the broken or worn parts are replaced before the belt or chain jumps too far, a lot of repair expense can be avoided.
Thursday, May 21st, 2015 AT 8:27 PM