Car Won't Start!
 

I have a 06 Evo IX and I put in a new battery (shuriken mini battery) the other day but i didnt start it till today. I turned it on and let it idle for a few seconds while I went to open my gate. Inside my car was scorchering hot so I turned on my AC and reversed my car out (stereo on too). After I reversed my car out I noticed my RPM's began to drop below .5 So I pulled back into the garge and let it idle a bit more and it died off by itself. Since I had to go somewhere, I used another car and left it sit for a few hours. When I came home I tried to start the car but it wouldn't start. So I checked the plugs, battery, battery cables, fuses, fuel relay, and added more grounds. After I added a few more grounds I tried to start it again, and it only started when I pressed the gas. When it started it seemed to be doing fine so I let it idle to check the voltage and it was 14V, after everything seemed fine I turned my Stereo and AC on and i noticed the Voltage dropped significantly and my RPM's began to drop. I think it's my alternator, but I'm not sure and I dont want to buy one if I don't have to. Any help is much appreciatedX.X BTW Ive was running an 1200w amp(for 6 months) too so I disconnected it too see if it would start but it didnt make a difference at all.

Check your clutch pedal switch

car needs to relearn iac positions. if u replace the battery all the learned values are gone. 1st thing i would do is turn the key to on position and let it sit their for 1 to 10 min. start it by stepping on the gas pedal. as u said it starts when u press the gas pedal. after starting let the gas pedal slowly so it idles and then let it idle for few minutes. if it still dies. check IAC value. or before u do that pop the upper intercooler hose by the TB and try to clean the TB with gum cutter or some kind to cleaner with a rag or paper towel. as the rpm drops below 500rpms voltage will drop.

Yes, as Aman stated, your car needs to relearn idle values.