A customer brought in a 2007 Subaru Legacy with the 2.5L 4-cylinder EJ25 engine. The owner complained of an engine vibration. From the initial description, it sounded like a pretty typical misfire issue.
If the problem turned out to be a classic misfire, the three basic things to check would be the compression, fuel, delivery and ignition for each cylinder, but before any diagnosis is started, you have to make sure you get as many details as possible from the vehicle owner, so naturally the owner was asked for a more complete description of when the problem occurred.
It turns out that about six months prior, the customer had the vehicle at another shop and the engine was overhauled. It was immediately after that the problem began.