3VZ-E is a terrible engine. But anyway...
The Start Injector Timing Switch aka cold injector time switch is probably bad, causing the engine to flood. I believe it is the sensor near the fuel pressure regulator (end of the fuel injector rail) but I don't remember exactly I have not worked on one of those engines in years.
edit -
go to page 524 of this service manual (.pdf document) it shows how to test the switch.