I've had my 02 Grand Prix 3.8 for a few years now. I just had the mass air flow sensor replaced and all of a sudden I have new problems. The first start of the day starts fine. Every other time I go to start my car it gives me problems. Usually it won't start on the first try but the second try usually gets it. It idles rough after I start it but while I am driving I have no problems. It's been warmer here the last couple of days and I haven't been having the starting issues just the idling like it's going to die but never does. My fuel filter and regulator have been changed. It is giving a code of P0420. It's drinking gas like crazy. I'm told it is most likely my catalytic converter but no one has ever heard of that be associated with starting issues. Could it be the 02 sensors?
