UNKNOWN specific failed component. Immediately after fuel-injector-seal replacement by an independent repair shop, the engine was running rough. I drove less than 0.1 mile, parked about 10 minutes, then restarted the car. I heard an abnormal rapid ticking/grinding mechanical sound. With my foot on the brake, I shifted from Park into Reverse. The car immediately accelerated backward with what appeared to be full engine power. I did not intentionally depress the accelerator. I attempted to stop with the foot brake, but the car continued with substantial force, jumped curbs and struck a fence. I used the handbrake and shut off the engine; I also recall shifting into Neutral. Three tires and multiple wheels were damaged, the car sustained major body damage and was declared a total loss. No one was injured, but pedestrians, other vehicles and a nearby building were at risk. The incident was captured by a security camera. BMW of Palm Springs later found no reproducible mechanical cause. It noted a loose floor mat after the collision/towing and said it “may have caused the complaint,” but did not establish causation. I reported the incident directly to BMW North America. The representative suggested driver error and emphasized that the preceding repair was not performed by a BMW dealer. I was not offered an engineering investigation, follow-up path or case number. My insurer considered but declined an independent engineering examination. The vehicle was later disposed of, so the sus