I did a minor tune-up on my vehicle this past weekened; plugs, wires, distributor cap, rotor, cleaned throttle body. Air temperature this morning was about 65 degrees and when the vehicle was started up it ran at normal idle, not high idle as I would expect. It ran kind of iffy for the first minute or so of driving, and the tachometer dropped down to 500 (almost stalled but didn't) twice within the first mile of driving, then when I came to the first stop idle speed was right on 850 or so where it normally is. Is there something I need to check (or that I missed) that is causing it not to idle high while the engine is cold on a chilly morning?