Hyundai Repair: 2001 Sonata engine light on, advance auto parts, emission control system

Question
The "check engine" light in my 2001 Sonata (4 cylinder) came on recently and I had diagnostic checks at both Advance Auto Parts and AutoZone.  The printout from AAP stated, "DTC (Codes) P0301 Cylinder 1 Misfire Detected" and "DTC Pending (Codes) P0446 EVAP Emission Control System Vent Circuit Malf."  The first code also came up again under pending.  From AZ, it states, "Troubleshooting P0446: The PCM has determined that a  malfunction exists in the electrical circuit for the vent control in the evaporative emission control system."  It goes on to say, "Definition: EVAP (Evaporative Emission System) purge/vent solenoid circuit condition; Explanation: The solenoids and system wiring are monitored for opens or shorts; Possible Causes: 1. Purge or vent solenoids defective, 2. Check connector and wiring, 3. Fuel saturated vapor canister, 4. Failed EVAP vent solenoid."  Can you help me detect what the specific problem may be and what parts I would need to fix it?  Please respond.  

Answer
You'll want to first concentrate on P0301.  That's the code that's occurred more than once.  Most misfires are caused by secondary ignition system components (spark plugs, plug wires, ignition coils).  Since you know it's cylinder #1, check the plug, wire and coil associated with that cylinder.

P0446 indicates that the ECM has detected excessive vacuum in the fuel tank.  This can occur for any number of reasons, including overfilling the tank.  The fact that this is a pending code indicates it has only occurred once.  Before beginning a painstaking diagnostic process, I'd recommend clearing the code and performing diagnosis only if it returns.  In that case, if you follow-up, I'll try to provide you with a diagnostic process and some common issues.