Eclipse can't swim

Last month my 18yr daughter decided to take her Eclipse through some water running across the road. She had a cold air intake and it went completly under the water. This caused the motor to be sucked full of water. When I opened the butterfly on the intake the water was sitting level in the intake. I got the water out and changed the oil and by some miracle it started. Since then, when she stops at a stoplight the idle slows down to almost nothing. It doesn't quit though. Then it surges up. When it does this there is a little bit of black smoke come out of the exhaust. Her gas mileage has dropped from 21 to 15. Had it scanned at Autozone. That showed random cylinder misfires. They suggested replacing the coil pack. Is this the first thing to do ? Thanks

She has a 98 non-turbo.

Check the plugs first and the wires, if it keeps doing that then I would recommend going with what autozone said.

My guess is that you fried something electrical under the hood when she went through the water. First check plugs, wires, and coil pack. Make sure there is no water sittin the the spark plug wells. After that, check the o2 sensor and the idle control sensor. If you really can't figure it out, take it to a dealer and have them run a quick diagnostic test.

I also recomend replacing the plugs and wires. Random missfire codes are 90% of the time those two parts. Coil packs should throw a specific CEL code.