Hot idle problem. Ask garage to chech coolant temperature sensor, coolant system. of cource, you need ask to check idle speed sensor. Because of above, the mixture either too rich or too lean.
Tips,
If you have air condition, next time, when you are in heavy traffic, turn A/C on to force fan turning.
Coolant temperature sensor feeds ECU aka computer the signal of engine temperature. If ECU gets signal saying it;s too hot, it reduces the mixture of gas. Too rich or too lean mixture make engine stall.
But this part is difficult to chek. As mentioned, other sensors also bring this problem. Sometime, for certain car, when you re-start after stall, the problem gone for a while, because you basically reset ECU.
DonCherry, thank you for your answer.It makes sense.
I have ever been to the garage and told them the symptom. They could not figure out the real problem. Firstly a vacuum leak was suspected, but no leak was found.
Actually, how to carry out the probe? Will it cause big problem if it does not get fixed? How much to fix it, i.e. to change the coolant temperature sensor?