What would cause a back fire through the intake?

 

Under what conditions does it backfire?

 

1) did you fix the vacuum leak you mentioned in your other post,?

2) any codes?

 

Have you recently done any work or changed something or it has ran great in the past and today you went to start it and it was backfiring out of nowhere? The reason is that most of the time, if it ran ok...it just doesn't start backfiring on its own one day to next unless possibly you filled up with ****ty gas yesterday...or has it always been backfiring?