1999 Isuzu Rodeo Question Mass Air Flow

I was told my MAF needed to be replaced. I disconnected it and removed it to see the internal condition. It looks extremely clean. I did nothing and reinstalled it. After reinstalling it the SUV would die out immediately after starting(wont idle), but if I gave it gas it would blow out lots of black smoke. I disconnected the battery for a few minutes and then reconnected it. Now everything seems to be fine. It idles fine and no more black exhaust smoke. I have not taken it for a drive yet. Is this normal and why would it now idle just fine? Oh, the check engine light is now off also.
Thanks