ideling issues

Ok. I have my 01 kia rio for two years and it
has had its fare share of kia problems. Last
night i went to crank my car and it just
clicked and lost all power, the battery cable
was loose. So i cleaned it and put it back on.
Now when i crank it. it wont idle unless u
keep the rpms up alittle and put in gear and
feather the gas for about 1 min. Then its
fine to drive anywhere. But as soon as u
turn it off and try to crank it again same
problem it has done this before but not for
this long. The last time i drove it about 5
miles and it cleared up and that was 5
months ago. And another wierd thing is the
car runs bad and get bad gas mileage until
the check engine light come on. It has done
that sence i bought the car idk why but it
just does. If anybody has an idea plz let me
know. Thanks