Hyundai Repair: Warning light, rich mixture, secondary ignition

Question

-Thanks. But why does it only happen in the early cold morning and then it's ok the rest of the day?------------------------------------------
The text above is a follow-up to ...

-----Question-----
I have a 2002 Sonata, v6, .On real cold mornings, after a few miles, the "check engine" light goes on and the car runs real rough, particularly on hills. This goes on for about 5 or so miles and the light goes out and the car runs smooth again. This morning (very cold) it lasted about 10 miles and then went out and ran smooth again. Any ideas? Thanks.
-----Answer-----
Based on the runs rough uphill description, I'd surmise that it's most likely you have a misfire.  Most misfires are caused by secondary ignition components (plug wires, spark plugs, ignition coil).

A misfire is just one of many things that will cause the check engine lamp to illuminate, however.  Your best bet is to have the engine and transmission trouble codes read.  If you follow-up with the trouble codes, I can tell you what they mean.  AutoZone and AAMCO have advertised they'll check the trouble codes for free.

Answer
It's hard to say without looking at the car.  It could be due to the rich mixture, thermal expansion of connector terminals, moisture level in engine compartment, etc.  It's possible you won't know the real answer until the diagnosis is complete.  And it's also possible you'll never find out why it only happens when cold.

Reading the trouble codes is still the first step.  You'll get the largest amount of information from knowing what they are and what they mean.