Coolant intrusion into cylinders causing engine misfires, spikes in engine temperature, and issues with car starting. The check engine light came on as I started the car, and the engine shuddered as if misfiring. As I was driving the vehicle to get the issue checked out, the vehicleas extreme temperature warning went off, instructing me to pull over and shut the vehicle off immediately. The coolant reservoir was found to be empty. After replacing the coolant, the car had difficulty starting. After finally getting the vehicle to start, I got it to a service center where it was diagnosed with a blown head gasket and coolant was present in the engine oil. I was informed that the vehicle WAS NOT safe to drive and needed a complete engine replacement.