Check Engine And Temp Light Flashing

I Have An 89 Le Sabre That When I Start It The Check Engine And Temp Lights Start Flashing And The Engine Runs Rough And Dies On Me But When The Lights Go Away The Car Drives Normal And This Happens While Driving Also Can Anyone Help Me With This Please.

Check to see that when the car is idling that the fan is on/off. also, I would suggest a new coolant temp sensor. It is located Pass. side just behind the manifold with yellow and brown wires :)