Why is my engine shaking during idle at stops and park?

I got a ford 1999 taurus SE with 100,000 miles on it. I just changed the spark plugs and wireset out and it got even worse. I was thinking the IAC might of just gone bad but before I go get one I wanted to ask if there was anything else I could test before buying more new stuff for it.

How's the integrity of your motor and transmission mounts. If they are original they are toast and need to be replaced as soon as possible.

Did you check/set the gaps on the spark plugs?

Also, cheap sparks plugs & wires can make your car run worse.

How to Gap Your Spark Plugs
http://www.dummies.com/home-garden/car-repair/electrical-system/how-to-gap-your-spark-plugs/

Before you spend a lot of money on parts you think might be the problem check all the hoses and clamps. In a car that old hoses will crack and a vacuum leak will cause your car to behave as you stated.

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