1999 Honda Civic Car stalls at idle speed

My girlfriend had a 1999 Civic LX with 136000 miles. The vehicle shutters when reverse is engaged. The civic also stalls while opperating the vehicle at idle speeds. This stall is most frequent when the civic's AC or defrost is running. There is no check engine light on her dash.

I changed out fouled spark plugs, a filthy AF, and cleaned throttle body. The fuel filter has recently been changed aswell.

Please help me to resolve this issue.