The main reason was the ECU wasn't properly tuned. The other reason could be some vacuum lines or MAF sensor were leaked/loose on the intake pipes. Try to disconnect the battery (both positive & negative) for 1/2 hour and reconnect it. If not, diagnose the code and see what it reads. I think Autozone can diagnose the code for free. Otherwise, you may get a manual and follow the instruction the find the code, or take your car to a shop.