Don't hold me to this but it could be the air intake temp during open loop startup. The ATS sensor in the air cleaner box on 2.8's. Not sure at what temp the air has to be for a 1500 rpm idle. During warm weather the startup idle seems normal at 900 rpm.
If I'm wrong about this I'm sure the guru's will be along shortly with the tar & feathers.
"Kilgore Trout once wrote a short story which was a dialogue between two pieces of yeast. They were discussing the possible purposes of life as they ate sugar and suffocated in their own excrement. Because of their limited intelligence, they never came close to guessing that they were making champagne." - Kurt Vonnegut