How do I reset the theft system in my 1999 Chrysler Sebring Convertible

Unlock with fob or door key, start as normal. Does the red dash light blink when key is inserted to start? That confirms programmed key code, allowing start and run. Check your manual for specifics. If manual lost mopartechauthority.com to order one. As far as engine rough running, when was last service, and what is mileage? Have garage run diagnostic to reveal any codes. Is spark ok? Check/replace wires, plugs, cap, alternator, battery. Air filter clean? Exhaust, including muffler, cat converter, sensors, pipes clear, operational? Fuel filter clean, tank clean, gas fresh, fuel pump strong? At 15 years old, a thorough assessment is due, there may be internal wear issues, crankshaft, valves, transmission, etc. Cheers!