From the MD80 Emergency checklist:
ENGINE FIRE/SEVERE DAMAGE OR SEPARATION
Throttle (affected engine) IDLE (Memory item)
1) If engine fire handle remain iluminated or severe damage or separation is suspect
Pull the engine fire handle and a lot of things.
2) if engine fire handle light TURN OFF or no severe damage or no separation
CONTINUE FLIGHT AT IDLE POWER and let the captain do whatever he wants