Does anyone know what conditions must be satisfied in order for the computer to purge the vapor canister? I'm wondering if the coolant temp never getting high enough due to a bad thermostat could have been a factor in getting evap system failure codes.

I'm pretty sure it does it at startup.

Most of the time, my blazer's engine starts more abrubtly than what I would consider normal from my experience with most other vehicles. It's not a crank crank crank vroom, or even a crank crank vroom... it's more like a cra VROOM kind of start (to try to put it in words). Does this sound normal to you, and if not, do you think it might be related to the evap system trouble code? Thanks a bunch for being available through AF, by the way... I'd like to see a number for all the dollars saved by the good advice that get's distributed through this medium.

Nothing wrong with a fast starting engine.

Mine does the same thing especially when it is full.

Just means your engine is getting the fuel it wants.

Right on! If it ain't broke . . . . . Don't fix it!