QuestionI failed the emissions test today and the printout indicated two OBD trouble codes: P0303 Cylinder 3 Misfire and P0442 Evaporative Emission Control System Leak. What needs to be fixed? Are these two problems related? I have a 2002 Hyundai Accent with 89K miles on it.
Thanks!
AnswerThese problems are unrelated.
P0303 indicates a misfire on cylinder #3 as you've stated. The most frequent issues causing misfires are with the secondary ignition system (spark plugs, wires, coil). If you've still got the original plugs and plug wires on the car, they probably need to be changed; the recommended interval for spark plug replacement is 30,000 miles. This problem could also be related to a problem with the #3 injector or a mechanical issue in the engine.
P0442 indicates a small fuel vapor leak. This could be due to an improperly installed fuel cap, a partially stuck open purge valve, or a fuel vapor leak anywhere else in the system. The two items I mentioned, along with a split fuel vapor hose at the purge control valve are all common occurrences.
If you're unable to check the car yourself for the above issues, I'd recommend taking it to a well-regarded shop that has an excellent reputation for being able to correctly diagnose and repair check engine lamp issues. In fact, the dealer may be the best place for this. The dealer's scan tool will be able to command the evaporative self-test to run, meaning they'll be able to check the system to verify whether the problem is currently present. If not, it's likely it was simply an improperly installed fuel cap.
