2000 jimmy 4.3 litre no turbo

Good morning,

I assume you mean backfiring.

This happens when a spark occurs when it should not. It could be a distributor cap, ignition wire, or lean or not enough fuel.

Is the check engine light on?

https://www.2carpros.com/articles/checking-a-service-engine-soon-or-check-engine-light-on-or-flashing

I attached a guide for you to read for this issue.

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

Let me know if you have any other questions.

Roy