Land Rover Repair: Discovery II 2000 Misfire, blown head gasket, vacuum leak

Question
I just took my disco II  with 90,000 in for service because the service engine light was on and the engine was idling rough. The dealer said the code that was set had to do with a misfire in the #4 cylinder. They replaced faulty plug wires and thought that may take care of problem. After a couple days the service light is on again so I replaced the spark plugs and that seem to get rid of the miss. After disconnecting battery the service light went out but after driving vehicle a few miles the light came on again. Could there be another problem such as the ignition coil or sticky exhaust valve. What should I do next?

Answer
First, the check engine light might have come back on for something different, the fault codes will have to be read and see if it's the same problem. If the check enginelight 'flashes, that indicates a misfire for sure (was it flashing?). Of course, the ignition coil pack and sticky valves could be weel the problem if the engine still has misfire problem. Of course, the whole enigne control will have to be checked to determine the exact cause since they may also can cause misfire problems (MAF, vacuum leak, blown head gasket etc.)