Engine stuttering and backfiring?

Hello,

An engine will backfire when there is unburnt fuel gets combusted either in the intake manifold or in the exhaust. This is typically due to the engine running rich.
This can be if the spark plugs are weak and unable to burn the fuel at the combustion chamber. Also, this could be for having too much fuel out of the injectors that the plugs are unable to burn all of it.

Here is a helpful article:

https://www.2carpros.com/articles/engine-backfires-while-running

Inspect the spark plugs for wear and gap. They should be gapped at .054 in.

It would be a good idea to test the fuel pressure as well. As too much fuel can cause backfire.

https://www.2carpros.com/articles/how-to-check-fuel-system-pressure-and-regulator

Please let me know of any questions.
Thank you.