Put a new battery in. Now will nott idol unless the airconditioner in on high on 2008 Mitsubishi Endeavor

When the air is off the car dies

2 answers
test electrical system you have something steeling pwr from your ignition system
The computer needs to relearn the idle speed. Take the car on a long drive with the A/C off. Lots of 40MPH plus. It will relearn after 10-15 miles.