87' 560SL high idle-sometimes

[biggiefl]

I have a cherry 560SL with 81k on it. Last week the battery was low so I put it on a charger overnight on trickle. Started up and ran great. Drove it a 10 miles to a friend's where it sat for a couple hours during Buc's game. Went to another friend's where it again sat for an hour or two. Started it up and she was idling at 1500+. Took it home and disconected battery for a few minutes thinking it would reset any codes even though no idiot lights are on(yes they all work). Started it up and same thing.

Next morning started it up and ran fine. Went to friend's house and let it sit an hour or so and when I started it she went to 1600rpm. At first I was thinking a vac line but they do not "fix" themselves so now I assume it is a sensor of some sort...Temp? Charging? cold start injector???? This car has only been driven 2k miles in 3 years but gas has stabil and inj cleaner. This is in roughly 60-70 degree weather as well(FL).

Any help on what to check would be greatly appreciated.

Nick