Backfiring
'94 Southwind 454 TBI. When climbing hills just before downshift from overdrive when the engine starts "lugging" it sometimes backfires. After downshift it runs "OK". Engine has 41,000 miles and ra...
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Along with what others have said, it's been my experience that bad spark plugs (or wires) can cause backfiring under heavy load like heavy throttle just before it down shifts.
