I will have a weekday meeting in Kuala Lumpur near the central train station that ends at 12PM. I will fly out of KUL with Malaysia Airlines at 4PM.
Assuming I leave on time and check in at the KLIA train station, will this be sufficient time?
Yes. It will take less than 1 hour, by train, to get from city center to KUL. That leaves you with three hours which is more than adequate for an international flight.
The biggest concern will be the time it takes to get to from your meeting to the train station. Another thing you should consider is how your luggage will encumber you.