Idle problem on 1996 Mercedes-Benz SL600

I received the car with an empty tank of gas.I filled it up with 93 octane & a bottle of Lucas engine treatment.I then drove it to a laser wash.The vehicle performed great until I got home & placed the car in park.The tach started moving from 650 rpm's to app. 1300rpm's all on its own.It will only do this once the car is at normal operating temps.HELP!

1 answer
i suggest you clean iac motor and recheck again