My Vitz 2007 is showing some problems while idling, initially it was having hiccups on when i used to press pedal on a signal opening but now more than often the engine just shuts down then i have to start it again and then it works fine but this only happens in initial 10 to 15 minutes of driving after that may be the car warms up or something and there is no such issue. there is no missing or any thing while speeding, it only shows this behavior while its idling.
the car starts instantly.
there is no water reduction in radiator.
i have a small OBD scanner and the errors its showing are 1603 and 1604
i took it to toyota thrice, they took a trial did numerous stop and drive but not even once it showed any symptoms so they checked the plug wires and throttle body, wires were fine and throttle body was cleaned some 5 6 months back.
I did try the new euro 5 petrol but there is no effect of it yet.
so any idea what it could be?