Q: engine dies after warming up

There are several components that can cause this problem. You are correct in thinking one could be the ignition system. Heat from the environment or the engine will cause the coils to expand, and not allow for the connection to be made. Most sensor issues can be detected by the ECU, and if you are able to run a scan for codes, a sensor may have tripped one. Unfortunately, you are looking at a process of elimination to diagnose this. If the issue is more complicated than the simple fixes you already considered, look next to the possibility of extra fuel getting into the system. If the vehicle is running rich, once the vehicle warms up it is less likely to properly burn the extra fuel. Its more like one of the other options we discussed, but a true diagnosis will need to be made after further testing.