My 2002 3RZ-FE engine pickup(190000km), started stalling occasionally on cold starts(sometimes hot as well but mostly cold) last year.
The engine starts up but stalls immediatley but then will start and run fine on the second attempt.
There does seem to be a bit of a rough idle when cold.
But if I disconnect one of the leads to the battery and leave it for an hour to reset the ECM the stalling problem and slightly rough idle disappears.
But after +/- 4 months its back?
Could it be a sticky IAC valve?

 

its a possibility, my 98 tacoma use to do that, then it stopped after i had a new tailpipe put on. i never figured out what it was exactly. my biggest possibility was the drainback valve in the fuel pump was bad. try priming it (cycle key on and off, don't start), 2 or 3 times, then start it and see

 

I've got the exact same problem with the same engine. Slightly rough idle and the other day it had a weird start up where the truck was about to stall before I turned it off. On the next start, it started up fine. Did you ever figure out what the problem was?

 

I sprayed carb cleaner in the IAC valve port in the throttle body with the engine running and I haven't had anymore problems.