I have a 2003 Avalanche. We have been dealing with weather in the -25 C (-13 F) to -40 C (-40 F) range, going almost two weeks now. Today, I started the truck about 15 minutes before moving (no plug in at work for the block heater). The truck felt more sluggish then I would expect, even for this weather. It stalls when at a low idle (which made for a very intresting drive home) but starts up again. I got my fingers crossed that it is just the three year old battery but....after doing some research and seeing all the potetial issues I think it might be the flux capacitor. But going to start with a thawed out battery first..