Another cause of this could be a Coil-on-Pack going bad. The Lancer uses a distributor-less system to send electricity to the spark plugs. There are two coil-on-packs above the 2nd and 4th spark plugs on top of the motor, each controlling 2 spark plugs. If one of those goes or is starting to go bad, you'll get an engine code, loss of power, and the engine will idle roughly, since it's only firing on 2 cylinders instead of all 4. They're about 90 bucks at an auto parts store, and only take a few minutes to replace. At the same time, I'd replace all the spark plug wires, and the set of spark plugs. The Lancer uses NGK Iridium plugs as OEM, I would definitely replace with those, as the copper or platinum plugs will give you a rough idle and power loss as well. All in all you can replace these in about 15-20 minutes with a 3/8" ratchet, extension bar, spark plug socket, and a 10mm socket.