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A backfire is usually the result of either a fuel delivery problem, ignition timing, engine vacuum leaks, or an internal engine problem.
Here is a link that explains how to check for and repair a backfire issue. See if it helps. If it doesn't, please feel free to let me know.
Let me know what you find or if you have other questions.
Friday, September 13th, 2019 AT 7:50 PM