1998 Hyundai Excel Excel 1998 warm engine: stalls, can't res

My car starts fine from cold starts in the morning and no problems under car temperature is running normal (warm). When it gets to norm temp, idling at red lights, car stalls. Can't restart until it's cooled. To avoid stalling, I maintain pressure on accelerator while in neutral position, it seems to work.
If I park a warm car, can't restart it till about 1 hour later as well.
I have brought to the mechanic, changed my coil pack, blew 200bucks. Problem still occurs. Mechanic taught me the spark plug test of attaching an external spark plug to the wires, result: no spark.
I guess this is an electrical fault? Or does it have anything to do with the crank position sensor or mass airflow sensor? - I got these from other posts on this website.
Thanks so much! :)