Engine das not keeping low rpm and going off

What is your question?

This happens first time after disconnecting battery for stack horn on Mitsubishi delarship replace some valve in excause system , then battery Yesterday I disconnected battery to fix bad connection in ground connector Now engine going off on low rpm RPM fluctuations between 800-300 that engine goes off Thank you so much

What makes this problem better or worse?

No difference

How long has your 2003 Mitsubishi Galant had this problem?

Happens in June - spend over 1000.00- valve cleaning, replacement, than new battery,now again