Mitsubishi Repair: Rough Idle into stall, negative battery cable, proper ratio

Question
I have a 2002 Eclipse, 2.4L , RS with automatic transmission. I just installed a cone intake on my car and now everytime I start the car it has a heavy rough idle and then stalls out. I just got a new battery recently and I can't think of what it could be! Thanks in advance!

Answer
Xavier,
Installing that new intake filter is now providing a lot more air into the engine than the car is used to.  The ECU (car's computer) is expecting a certain amount of air so it can regulate the proper amount of fuel to maintain a proper ratio for combustion.  You may have luck just resetting your ECU.  This can be done by disconnecting the negative battery cable for about 15 minutes.

You may want to have your alternator and fuel pump checked to make sure the are operating to spec.  The alternator should be putting out around 14.5 volts while the engine is running.  Your mechanic can inspect your fuel pressure and check if the fuel pump is operating properly.
Good luck!