Engine backfiring

Good evening,

I would start by checking the compression. It could be a valve if the compression is low.

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

https://www.2carpros.com/articles/how-to-test-engine-compression

It could also be a broken valve spring. The valve may not be closing all the way and it backfires out that cylinder. I attached a picture of the valve spring for you. Once one of the coils break, the spring will not have enough pressure to hold the valve closed.

Roy

Thank you Roy, I will do a compression test before I start pulling valve covers. Lee

You are welcome.

Let us know if you have any other questions.

Always glad to help.

Roy