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2004 Aveo intermittent misfire problem

My 2004 Chev Aveo has recently developed a strange misfire pattern. I am hoping to get some clues before I take it to a mechanic. It only misfires when at an idle and then again between 50 and 55 mph going up an incline. Above 55, it runs fine. Between 5 and 50, it runs fine. It has 109,000 miles and had the timing belt changed at 90,000. Any ideas of what would be causing this?

It sounds like a coil pack problem or a spark plug wire issue.

I agree. When was the last time the spark plugs were changed out?

I concur with both comments. A good mechanic will find this problem rather quickly.

Thank you for the help. I’ll have it checked out. Plugs were changed at 90,000, but I don’t know about the wires.