My 97 GT blew the heater hose on the intake . I reattached it and refilled with antifreeze and water . Now when I start it , it idles fine for about 2 minutes then start making a ticking noise from the exhaust and misses really bad . It keeps going back and forth from running fine the ticking and missing . Any ideas ? Never had any problems until this happened . It has a 2003 Mustang GT engine .