5-L SL 500 DEALER REPLACED CKANK SENSER -- STARTS PROPERLY COLD -- WARM UP FOR 20 MINUTS PLUS AND WILL NOT START- BACKFIRES THRU INTAKE AND EXHAUST . 1995 - 80 THOUSAND MILES -- DEALER SEAMS TO BE STUCK? I AM MECH. PERSON. AGE 68 -- THIRD OWNER. I TOOK IT TO DEALER FOR THIS PROBLEM. SUMMER CAR. I HAVE DRIVEN THE CAR AND IT JUST QUIT - HAD TOWED HOME. SOUNDS LIKE IT IS OUT OF TIME?