Mitsubishi Repair: 2004 mitsubishi lancer es, mitsubishi lancer, 2004 mitsubishi lancer

Question
why is it only while my lancer is in park the rpm gauge will shoot up and down almost till the point it shuts off.The battery and alternator where replaced but the problem  still consist.

Answer
James: I would have the car coded, see what the computer might kick out as to the problem with that. The computer controls everything in that engine, sometimes when things like this happens and can not be found. Doing a coding will explain it. Hope this helps and God bless: Linda