Sounds like a popping noise, almost like a misfire or slight backfire through the intake system or airpump area. Only does it when cold and I don't recall hearing it before. Goes away entirely by the time it is warmed up and the idle has gone down to normal rpm. Not terribly loud but can hear it from in the car. Any thoughts? Particularly if it is something that just started happening. Car runs great, no apparent problems with anything else. Thanks.