Tried the usual common solutions first like replacing the spark plug and/or ignition coil for the affected cylinder. Had a compression test done and cylinder showed no compression. Further investigation determined cause as a burned exhaust valve. Saw a claim made that the engine is supposed to last at least 500,000 miles without major issues. Turns out getting a shop to replace the valve would cost much more than the car is worth, so why bother? Also saw elsewhere that burned exhaust valves are actually fairly common around my mileage range for that particular engine. Been a great car up until this point. Will now have to limp around on 4 cylinders either until I get it the valve replaced (might as well replace them all) or get something new.