Runs fine when is cold. What could cause rpm stall on a 1999 Mitsubishi mirage 1.8 liter?

If the check engine light has been coming on, start with having the code(s) read. The code(s) will help you diagnose the stalling problem. Your local auto parts store can read the codes for you at no cost. When the engine is cold the ECM (Engine Control Module) runs the engine on a predetermined program also known as an open loop. When the engine gets up to normal operating temperature the ECM runs the engine on information it receives from various sensors, also known as a closed loop.