OMG need help fast

couple of possible causes that will need the valve covers removed to check two of and that be a wiped lobe on the camshaft or a broken rocker arm. as was mentioned timing chain jumped or a sunk valve from crappy gas. you can pull the spark plug wires one at a time form the distributor cap while the engine is running to determine which cylinder is not firing and then go from there. a compression test on all cylinders will be a help also