I found "Service Engine Soon" lights on two months ago. I checked the code (P0133) is about Oxygen Sensor problem. We continued to use this car for local shopping. One day about three weeks ago when I started the engine, the car vibrated obviously. Therefore, I turned off the engine for troubleshooting late on. When I came back to check the car a few days later, it can never been started anymore. I changed spark plugs, ignition wires, and I checked sparking for all cylinders. All of them are still firing normally. I think the problem is more related to the pressure. How do I go about further troubleshooting and solve the problem from here?