My 94 Honda civic idles very rough in gear. If I shift to neutral, smooths out? on 1994 Honda Civic

In gear, it idles very roughly, sometimes it will rev up and down. If I shift into neutral, it will immediately smooth out

Asked by for the 1994 Honda Civic
2 answers
check your Iac valve and for vacuum leaks
agree with goodguy also ck for misfires