What are the common engine problems with a 2005 Cadillac STS

Hello, I'm not sure what you mean by a knocking noise from bad gas. A spark knock, like pre-ignition? Knocking resulting in the engine stopping -- this sounds like a possible catastrophic engine failure. None the less, testing must be performed to find out if your engine is binding and locked up, or if you have an engine performance issue that needs to be resolved. www.repairpal.com/repair-shops