On occasion (maybe once every other month or so) I hear a loud, violent, quick "bang" while I'm rolling to a stop or at full stop. It sounds like it's coming from the engine compartment but cannot be sure. It happens without any warning and feels like someone just tapped into my rear bumper. Could it be a sporadic spike or drop in brake pressure or perhaps the A/C compressor locking up? The engine runs pretty smoothly
and I recently replaced timing chain so I don't think anything in the engine is slipping. Any ideas out there (I'm stumped)???