In the morning, my truck will shoot up to 1500 rpm instantly, then drop to 1100 rpm within 2-3 seconds. It will then drop down to 600 rpm gradually as it warms up. I let the truck warm up for about 1 minute before taking off. I live in Wisconsin so we have the same kind of mornings. Driving down the interstate at 65, my truck will tach about 1800.