I have a 99 Pont Montana w/ auto trans. When engine is warming to driving temp, it misses, sputters, and even backfires (I think)when shifting from first to second gear. I can drive car by barely depressing gas pedal and she’ll slowly get up to speed. The car has to be driven about 2 minutes before this happens and once it is warm it behaves great. Any suggestions? I haver changed fuel filter, air filter and checked tranny fluid level.
Something you can do as a start is a good visual underhood inspection. Look for anything broken,cracked,knocked off,just anything out of place.
You haven’t mentioned any codes or maintiance items like plugs,or plug wires, we also could be talking about rodent damage.