1995 BMW 740i check engine light

1995 BMW 740i

My BMW has a check engine light on and it runs really rough at an idle. I smell a gaseous odor like it is “loading up” at an idle. What are the possible causes of this?

No reason at all to guess since the check engine light is on. Have the codes scanned and post the codes below in the comments. Just about any local auto parts store will scan you codes for free.