What are some 2002 Mitsubishi Lancer idle problems?

The most common reasons that a 2002 Mitsubishi Lancer will idle poorly are a failed or failing throttle position sensor, a bad idle air control valve, or a throttle body valve that's become excessively d***y. The latter is, of course, the simplest and least expensive to fix; You'll just need an approved parts cleaner and a little bit of elbow grease. In the case of a failed or failing sensor, You may want to check if You're getting any diagnostic trouble codes (DTCs). You can typically read these with an OBD-II scan tool -- if You don't have one, they're typically offered for use free of charge through most major automotive part stores. Once You have a DTC (if applicable), You'll narrow down Your diagnosis possibilities tremendously.