Been getting on340 and po344 can sensor codes since I got my 2006 expedition but never have found a cause. Found a post on here that a bad alternator could be the cause? Also once in awhile it will misfire at highway speed but not ever throw a misfire code, you can feel the vehicle jerk. Just recently started misfiring causing it to shudder and also seems to try to die. Getting po307 misfire on #7 , changed coils but didn't help. Don't believe it's a plug. I am hear a new noise near the #7 plug kind of a repeating sucking sound, wonder if the injector could be making it? Really hoping it's not a bad valve or intake gasket.