I have a gas hot air Carrier furnace with electronic ignition, manufactured in 1989... model 58SX080-66-1. Sometimes when it lights it backfires and knocks the panel off as well as opens the door to the flames. My guess there is not enough air mixing with the gas... an I right and if so how do I fix this? There was also water leaking all over the floor but I resolved that by cleaning out the hoses etc. Now this! HELP!

Thanks
Linda

Dangerous, very dangerous,, get it checked out pronto, the danger is not worth the trying to save a few bucks

Electronic ignition... is it spark-to-pilot, or direct/hot surface ignition? What you describe sounds like delayed ignition. While potentially dangerous, resolving the problem can be quite simple in most cases.