Subaru Repair: Heat related missfire, coil pack, service engine soon light

Question
We have a '96 Impreza 2.0 & it develops a missfire in hot weather after travelling at highway speed for around 45 minutes.  After a little while the "check engine" lamp comes on.  Allowing the engine to cool for 15-20 minutes usually makes the problem go away but I'd like to fix it.

Answer
First off the best start to the diagnosis is find out what code the Service engine soon light is throwing.  If I were to guess tune-up the car with Genuine Subaru Parts, spark plugs, wires, fuel filter, pcv valve.  You could also try a new coil pack, a coil pack can get hot and stop working. When it cools it starts working again.  Hope I could help you!