grabbed this info from a smart ass dude on awdpirates.net
The reason we have trouble starting with E85 in colder weather is simply because it does not evaporate at the same rate as gasoline. The "cutoff" point to where it starts getting ****ty seems to be somewhere around 50' F, and evaporates less and less (obviously) as the temps drop from that point. Because there's only 15% gasoline in E85, at lower temperatures there is less vapor in the cylinder, which makes the AF mixture harder to ignite.
Your ECU has several tables in it whereby it will start adding fuel as the coolant temperature drops, to compensate. This becomes more important with E85, but there's also a fine line where adding TOO much fuel during cranking will saturate the cylinder and snuff out the spark.
Block heaters do help, this is a fact, but what it all comes down to is simple physics, and finding that sweet spot where you spray just the right amount of fuel at the right temperature to get the engine to start with minimal fuss."