i have a 3.3 engine. i’ve been getting backfire from the exhaust. it just happens the first time it’s driven in the day. usually when i’m going up a hill it’ll start backfiring & continue for about a mile then it’s fine for the rest of the day. it lost all power going up a long steep hill 1 time. i changed the rear o2 sensor with no change in the problem. any ideas???
Tell us why you changed the rear O2 sensor. Was (is) your check engine light on?
Well, a backfire indicates unburned gas in the exhaust. Since it’s just at the beginning of the day’s driving, I would look for a fuel injector that’s leaking and filling up a cylinder with raw gas overnight. It might take a mile or two to purge the exhaust system of all this extra (and liquid) gas. If someone pulls the spark plugs in the morning (before starting up), they could pretty easily see if one or two cylinders were full of gas. By any chance is extra smoke involved with all this?