TURNED ON IGNIION KEY OF 1998 BUICK PARK AVENUE TO START AND HEARD LOUD BANG AND THEN NOTICED GREY SMOKE AT REAR OF HOOD AREA. TURNED OFF KEY, GOT OUT AND CLOSED DOOR, PROCEEDED TO HOUSE TO CALL 911 AND GOT KITCHEN FIRE EXTINGUISHER. I WENT BACK TO BURNING CAR, OPENED HOOD, OBSERVED FIRE AT SIDE OF ENGINE NEXT TO FIREWALL. I USED FIRE EXTINGUISHER TO GET MOST OF FIRE OUT. THERE WAS SOME FIRE UNDER ENGINE ON GROUND WHICH THE EXTINGUISHER DID NOT GET OUT. THE EXTINGUISHER WAS NOW EMPTY SO I WENT BACK TO HOUSE AND GOT BAKING SODA FROM KITCHEN AND THREW IT UNDER ENGINE TO EXTENGUISH THE FIRE UNDER THE ENGINE. FIRE DEPARTMENT CAME BUT I HAD FIRE OUT BY THEN.