What Is Some Reasons That A Car May Idle Hard While Stopped In Drive

I drive an 03 Hyundai Sonata with a 4 cylinder engine. I was always told rough idling means it is time for new spark plugs. According to my maintenance schedule it is quite a while before I need to get new spark plugs (30,000 miles off)

What else could be the problem?
Thanks in advance
The AC does contribute to the rough idle, but I have driven with it off, and I still get the rough idle.

Answers for The Question

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