I have a 1994 2500 with a 5.7. It has the Throttle Body Injection. When I am decelerating or especially idling down a long hill in a low gear so I will not go to fast my truck will backfire very loud. Not just your normal small little backfires that you will usual get. But loud bangs about every 4 to 5 seconds. Im suprised my muffler isn't blown up yet. Is my truck running rich. I'm told you can't adjust a TBI. Could it be I am not running a correct spark plug. Maybe I could use a hotter plug. I am also getting terrible gas mileage. Mabye they both are caused by the same problem. Any help would be great. Thanks.

 

My 92 4.3 S10 Blazer does this. Turns out the fuel pressure was not correct. I r&r'd the fuel pump and it ran fine. My dad then insisted on replacing the wires and it's doin it a little bit. Dunno why.

 

Thanks. I'll check the fuel pressure. I ran out of gas a while back and the truck ran terrible for a couple days. Mabye I messed it up. Thanks.