Is the check engine light on? If yes, have the engine computer scanned. Unfortunately you are in California and in that state Autozone WON'T provide the free service that they do in the other 49 states. CARB told them they can't. So you'll have to go to a mechanic and pay upwards of $40 to $60 just to have them connect up a code reader and pull the code. That code can really provide important details as to what the problem is.