Engine backfire

Porkchop

New Member
Joined
Aug 3, 2020
Messages
1
Location
New York
Hey guys, I’m fairly new at mechanics so forgive my mistakes.

I just did an engine tune up on my ‘88 yj. (4.2L). Before the tune up she was struggling to stay running and required start fluid after not running for more than 2 days. After the tune up she had a nice consistent idle to her but she would sometimes backfire on start up. I’m confident I did the tune up correctly.

Can anyone guess why it would backfire on start up?

(it never backfired before this)