Starting Noise

[Daylindafung]

I am not sure if this is a big problem or not.... When I start my car in the morning in this cold weather, my 2012 mazda 3 sky is very loud in both the engine and the corksport catback. But suddenly this past week (colder weather), whenever I start my car, it is so quiet. After maybe 2 mins of idling quiet, it goes back to normal start sound and becomes really loud for like 10 secs and quiets down again like normal. Anything I should really worry about?

[XTOTHEL]

After a cold start your engine should be at a higher RPM than normal, at least that's what I've noticed with mine (slow cranking, start to 2k+ RPM), thus louder :)

[ottoyu34]

Make sure your AC or defrost is not on.

[morganc]

Different ambient temperatures will cause the ECU to run at different operating points. Due to the deadening frequencies of the exhaust, different RPMs and fuel mixtures can be louder or quieter. Think about it this way; your engine noise can be super loud when accelerating, or quite when you let off the gas, even though you're momentarily at the same RPM. Just depends how much air/fuel and what temperature it's operating at.