Sounds like injector(s) leaking. Holding the throttle to the floor while cranking , puts it in 'clear flood' mode , which shuts off the injector drivers allowing the cylinders to burn off the excess fuel. do you see a brief cloud of smoke right after it starts and is it a little rough for the first few seconds? Have fuel system pressure checked , check for leaks externally , pull the plugs -probably fouled pretty good by now. If Vacuum operated pressure regulator pull the hose and see if it's wet with fuel. Just some random thougts....If you don't know how to check these yourself- definitely get it to a shop you trust for proper diagnosis.