02 4.0 backfires between 45-60mph

[JeffsTJ]

I have an annoying backfire at 45-60mph. it doesn't do it all the time. you can feel it in the floorboards sometimes so where do i start? i put a new cam and crank sensor on it when i first got it and they are not Mopar. also the check engine light comes on for weeks and it goes out for weeks. backfires happen in either case.

 

[Nimbley]

I’d start by replacing the sensors again with mopar sensors. Also check for vac leaks. A lean mixture can cause backfires at a light throttle such as holding 50 mph. Listen close. Usually a lean mix will also cause detonation or “ping” but timing would be my first guess. What’s the mileage on the engine? It’s possible it’s time for a timing chain.

 

[JeffsTJ]

I’d start by replacing the sensors again with mopar sensors. Also check for vac leaks. A lean mixture can cause backfires at a light throttle such as holding 50 mph. Listen close. Usually a lean mix will also cause detonation or “ping” but timing would be my first guess. What’s the mileage on the engine? It’s possible it’s time for a timing chain.

I’d start by replacing the sensors again with mopar sensors. Also check for vac leaks. A lean mixture can cause backfires at a light throttle such as holding 50 mph. Listen close. Usually a lean mix will also cause detonation or “ping” but timing would be my first guess. What’s the mileage on the engine? It’s possible it’s time for a timing chain.

The mileage is 81k. I drove it to work today running around 65mph and no backfires. It’s about an 85 mile round trip.